Added solver & optimized state.

Positions are kept by index only.

cmd/krampus19/animations.go

@@ -14,9 +14,8 @@ type moveAnimation struct {
 	pos      geom.PointF32
 }
 
-func newMoveAnimation(e *entity, to geom.Point) *moveAnimation {
+func newMoveAnimation(e *entity, from, to geom.Point) *moveAnimation {
-	ani := &moveAnimation{e: e, from: e.pos, to: to, pos: e.pos.ToF32()}
+	ani := &moveAnimation{e: e, from: from, to: to, pos: from.ToF32()}
-	ani.e.pos = to
 	return ani
 }
 

cmd/krampus19/entity.go

@@ -2,11 +2,12 @@ package main
 
 import (
 	"opslag.de/schobers/geom"
+	"opslag.de/schobers/krampus19/soko"
 )
 
 type entity struct {
-	typ entityType
+	id  int
-	pos geom.Point
+	typ soko.EntityType
 	scr entityLoc
 }
 
@@ -15,6 +16,6 @@ type entityLoc struct {
 	z   float32
 }
 
-func newEntity(typ entityType, pos geom.Point) *entity {
+func newEntity(e soko.Entity, pos geom.Point) *entity {
-	return &entity{typ, pos, entityLoc{pos.ToF32(), 0}}
+	return &entity{e.ID, e.Typ, entityLoc{pos.ToF32(), 0}}
 }

cmd/krampus19/entitylist.go

@@ -1,35 +0,0 @@
-package main
-
-import "opslag.de/schobers/geom"
-
-type entityList []*entity
-
-func (l entityList) Add(e *entity) entityList {
-	return append(l, e)
-}
-
-func (l entityList) AddList(list entityList) entityList {
-	return append(l, list...)
-}
-
-func (l entityList) Find(pos geom.Point) int {
-	for i, e := range l {
-		if e.pos == pos {
-			return i
-		}
-	}
-	return -1
-}
-
-func (l entityList) FindEntity(pos geom.Point) *entity {
-	idx := l.Find(pos)
-	if idx == -1 {
-		return nil
-	}
-	return l[idx]
-}
-
-func (l entityList) Remove(pos geom.Point) entityList {
-	idx := l.Find(pos)
-	return append(l[:idx], l[idx+1:]...)
-}

cmd/krampus19/entitymap.go

@@ -0,0 +1,25 @@
+package main
+
+import "sort"
+
+type entityMap map[int]*entity
+
+func (m entityMap) RenderOrder() []*entity {
+	entities := make([]*entity, 0, len(m))
+	for _, e := range m {
+		entities = append(entities, e)
+	}
+
+	sort.Slice(entities, func(i, j int) bool {
+		var posI, posJ = entities[i].scr.pos, entities[j].scr.pos
+		if posI.Y == posJ.Y {
+			if posI.X == posJ.X {
+				return entities[i].id < entities[j].id
+			}
+			return posI.X < posJ.X
+		}
+		return posI.Y < posJ.Y
+	})
+
+	return entities
+}

cmd/krampus19/level.go

@@ -1,142 +0,0 @@
-package main
-
-import (
-	"errors"
-	"fmt"
-	"io"
-
-	"opslag.de/schobers/geom"
-)
-
-type entityType byte
-type tile byte
-
-const (
-	entityTypeInvalid   entityType = entityType(0)
-	entityTypeNone                 = '_'
-	entityTypeCharacter            = '@'
-	entityTypeEgg                  = 'X'
-	entityTypeBrick                = 'B'
-)
-
-func (e entityType) IsValid() bool {
-	switch e {
-	case entityTypeNone:
-	case entityTypeCharacter:
-	case entityTypeEgg:
-	case entityTypeBrick:
-	default:
-		return false
-	}
-	return true
-}
-
-const (
-	tileInvalid tile = tile(0)
-	tileNothing      = '.'
-	tileBasic        = '#'
-	tileMagma        = '~'
-)
-
-func (t tile) IsValid() bool {
-	switch t {
-	case tileNothing:
-	case tileBasic:
-	case tileMagma:
-	default:
-		return false
-	}
-	return true
-}
-
-type level struct {
-	width    int
-	height   int
-	tiles    []tile
-	entities []entityType
-}
-
-func (l level) idxToPos(i int) geom.Point { return geom.Pt(i%l.width, i/l.width) }
-
-func (l level) posToIdx(p geom.Point) int {
-	if p.X < 0 || p.Y < 0 || p.X >= l.width || p.Y >= l.height {
-		return -1
-	}
-	return p.Y*l.width + p.X
-}
-
-func parseLevelAsset(r io.Reader) (level, error) {
-	var l level
-	ctx := levelContext{&l}
-	err := parseLines(r, ctx.parse)
-	if err != nil {
-		return level{}, err
-	}
-	return l, nil
-}
-
-type levelContext struct {
-	level *level
-}
-
-func (c *levelContext) parse(p *lineParser) parseLineFn {
-	if p.eof() {
-		return nil
-	}
-	switch p.peek() {
-	case "level:":
-		return c.parseContent
-	case "":
-		p.next() // skip
-		return c.parse
-	default:
-		return nil
-	}
-}
-
-func (c *levelContext) parseContent(p *lineParser) parseLineFn {
-	if p.next() != "level:" {
-		return p.emitErr(errors.New("expected level start"))
-	}
-	return c.parseRow
-}
-
-func (c *levelContext) parseRow(p *lineParser) parseLineFn {
-	if p.eof() {
-		return p.emitErr(errors.New("unexpected end of file"))
-	}
-	line := p.next()
-	if line == ":level" {
-		return c.parse
-	}
-	if c.level.height == 0 {
-		c.level.width = len(line) / 2
-	}
-	return c.addRow(p, line)
-}
-
-func (c *levelContext) addRow(p *lineParser, line string) parseLineFn {
-	var tiles []tile
-	var entities []entityType
-	for i := 0; i < len(line); i += 2 {
-		tiles = append(tiles, tile(line[i]))
-		entities = append(entities, entityType(line[i+1]))
-	}
-
-	for i, t := range tiles {
-		if !t.IsValid() {
-			return p.emitErr(fmt.Errorf("level contains invalid tile at (%d, %d)", i, c.level.height))
-		}
-	}
-	for i, e := range entities {
-		if !e.IsValid() {
-			return p.emitErr(fmt.Errorf("level contains invalid entity type at (%d, %d)", i, c.level.height))
-		}
-	}
-
-	c.level.height++
-	c.level.tiles = append(c.level.tiles, tiles...)
-	c.level.entities = append(c.level.entities, entities...)
-
-	return c.parseRow
-}

cmd/krampus19/levelpack.go

@@ -4,12 +4,16 @@ import (
 	"errors"
 	"io"
 	"strings"
+
+	"opslag.de/schobers/krampus19/gut"
+
+	"opslag.de/schobers/krampus19/soko"
 )
 
 type levelPack struct {
 	name   string
 	order  []string
-	levels map[string]level
+	levels map[string]soko.Level
 }
 
 func (p levelPack) find(level string) int {
@@ -38,19 +42,19 @@ type parseLevelPackContext struct {
 
 func parseLevelPackAsset(r io.Reader, openLevelFn func(id string) (io.ReadCloser, error)) (levelPack, error) {
 	ctx := &parseLevelPackContext{}
-	err := parseLines(r, ctx.Parse)
+	err := gut.ParseLines(r, ctx.Parse)
 	if err != nil {
 		return levelPack{}, err
 	}
 
-	pack := levelPack{name: ctx.name, levels: map[string]level{}}
+	pack := levelPack{name: ctx.name, levels: map[string]soko.Level{}}
 	for _, id := range ctx.levels {
 		rc, err := openLevelFn(id)
 		if err != nil {
 			return levelPack{}, err
 		}
 		defer rc.Close()
-		level, err := parseLevelAsset(rc)
+		level, err := soko.ParseLevel(rc)
 		if err != nil {
 			return levelPack{}, err
 		}
@@ -61,65 +65,65 @@ func parseLevelPackAsset(r io.Reader, openLevelFn func(id string) (io.ReadCloser
 	return pack, nil
 }
 
-func (c *parseLevelPackContext) Parse(p *lineParser) parseLineFn {
+func (c *parseLevelPackContext) Parse(p *gut.LineParser) gut.ParseLineFn {
-	if p.skipSpaceEOF() {
+	if p.SkipSpaceEOF() {
-		return p.emitErr(errors.New("empty level pack"))
+		return p.EmitErr(errors.New("empty level pack"))
 	}
 	return c.parse
 }
 
-func (c *parseLevelPackContext) parse(p *lineParser) parseLineFn {
+func (c *parseLevelPackContext) parse(p *gut.LineParser) gut.ParseLineFn {
 	const levelsTag = "levels:"
 	const nameTag = "name:"
 
-	if p.skipSpaceEOF() {
+	if p.SkipSpaceEOF() {
 		return nil
 	}
 
-	line := p.next()
+	line := p.Next()
 	switch {
 	case strings.HasPrefix(line, nameTag):
 		c.name = strings.TrimSpace(line[len(nameTag):])
 		return c.parse
 	case strings.HasPrefix(line, levelsTag):
-		return skipSpaceBeforeContent(c.parseLevels)
+		return gut.SkipSpaceBeforeContent(c.parseLevels)
 	}
-	return p.emitErr(errors.New("tag not allowed"))
+	return p.EmitErr(errors.New("tag not allowed"))
 }
 
-func (c *parseLevelPackContext) parseLevels(p *lineParser) parseLineFn {
+func (c *parseLevelPackContext) parseLevels(p *gut.LineParser) gut.ParseLineFn {
 	const levelTag = "level:"
 	const levelsEndTag = ":levels"
 
-	line := p.next()
+	line := p.Next()
 	switch line {
 	case levelTag:
-		return skipSpaceBeforeContent(c.parseLevel)
+		return gut.SkipSpaceBeforeContent(c.parseLevel)
 	case levelsEndTag:
 		return c.parse
 	}
-	return p.emitErr(errors.New("tag not allowed"))
+	return p.EmitErr(errors.New("tag not allowed"))
 }
 
-func (c *parseLevelPackContext) parseLevel(p *lineParser) parseLineFn {
+func (c *parseLevelPackContext) parseLevel(p *gut.LineParser) gut.ParseLineFn {
 	const idTag = "id:"
 
-	line := p.next()
+	line := p.Next()
 	switch {
 	case strings.HasPrefix(line, idTag):
 		c.levels = append(c.levels, strings.TrimSpace(line[len(idTag):]))
-		return skipSpaceBeforeContent(c.parseLevelEnd)
+		return gut.SkipSpaceBeforeContent(c.parseLevelEnd)
 	}
-	return p.emitErr(errors.New("must have an id tag"))
+	return p.EmitErr(errors.New("must have an id tag"))
 }
 
-func (c *parseLevelPackContext) parseLevelEnd(p *lineParser) parseLineFn {
+func (c *parseLevelPackContext) parseLevelEnd(p *gut.LineParser) gut.ParseLineFn {
 	const levelEndTag = ":level"
 
-	line := p.next()
+	line := p.Next()
 	switch {
 	case strings.HasPrefix(line, levelEndTag):
-		return skipSpaceBeforeContent(c.parseLevels)
+		return gut.SkipSpaceBeforeContent(c.parseLevels)
 	}
-	return p.emitErr(errors.New("tag not allowed"))
+	return p.EmitErr(errors.New("tag not allowed"))
 }

cmd/krampus19/lineparser.go

@@ -1,64 +0,0 @@
-package main
-
-import (
-	"errors"
-	"io"
-	"io/ioutil"
-	"strings"
-)
-
-type lineParser struct {
-	lines []string
-	i     int
-	err   error
-}
-
-var errUnexpectedEnd = errors.New("unexpected end of file")
-
-func (p *lineParser) eof() bool    { return p.i == len(p.lines) }
-func (p *lineParser) peek() string { return p.lines[p.i] }
-func (p *lineParser) next() string {
-	i := p.i
-	p.i++
-	return p.lines[i]
-}
-
-func (p *lineParser) emitErr(err error) parseLineFn {
-	p.err = err
-	return nil
-}
-
-func (p *lineParser) skipSpaceEOF() bool {
-	for !p.eof() && len(strings.TrimSpace(p.peek())) == 0 {
-		p.next()
-	}
-	return p.eof()
-}
-
-func skipSpaceBeforeContent(next parseLineFn) parseLineFn {
-	return func(p *lineParser) parseLineFn {
-		if p.skipSpaceEOF() {
-			return p.emitErr(errUnexpectedEnd)
-		}
-		return next
-	}
-}
-
-type parseLineFn func(p *lineParser) parseLineFn
-
-func parseLines(r io.Reader, fn parseLineFn) error {
-	content, err := ioutil.ReadAll(r)
-	if err != nil {
-		return err
-	}
-	lines := strings.Split(string(content), "\n")
-	for i, line := range lines {
-		lines[i] = strings.TrimRight(line, "\r\n")
-	}
-
-	parser := &lineParser{lines: lines}
-	for fn != nil {
-		fn = fn(parser)
-	}
-	return parser.err
-}

cmd/krampus19/playlevel.go

@@ -3,11 +3,12 @@ package main
 import (
 	"fmt"
 	"log"
-	"sort"
+	"strconv"
 
 	"opslag.de/schobers/allg5"
 	"opslag.de/schobers/geom"
 	"opslag.de/schobers/krampus19/alui"
+	"opslag.de/schobers/krampus19/soko"
 )
 
 type playLevel struct {
@@ -26,6 +27,7 @@ type playLevel struct {
 	scale   float32
 
 	state       playLevelState
+	pathFinding bool
 }
 
 type keyPressedState map[allg5.Key]bool
@@ -121,13 +123,13 @@ func (l *playLevel) Layout(ctx *alui.Context, bounds geom.RectangleF32) {
 		l.offset = geom.PointF32{}
 
 		level := l.state.Level()
-		var contentCenter = l.posToScreenF32(geom.PtF32(.5*float32(level.width), .5*float32(level.height)), 0)
+		var contentCenter = l.posToScreenF32(geom.PtF32(.5*float32(level.Width), .5*float32(level.Height)), 0)
 		var content = geom.RectF32(contentCenter.X, contentCenter.Y, contentCenter.X, contentCenter.Y)
-		for idx, tile := range l.state.Level().tiles {
+		for idx, tile := range l.state.Level().Tiles {
-			if tile == tileNothing || tile == tileInvalid {
+			if tile == soko.TileTypeNothing || tile == soko.TileTypeInvalid {
 				continue
 			}
-			pos := level.idxToPos(idx).ToF32()
+			pos := level.IdxToPos(idx).ToF32()
 			bottomLeft := l.posToScreenF32(pos.Add2D(-1.5, 1.5), 100)
 			content.Min = geom.MinPtF32(content.Min, bottomLeft)
 			content.Max = geom.MaxPtF32(content.Max, bottomLeft)
@@ -166,6 +168,8 @@ func (l *playLevel) Handle(e allg5.Event) {
 			case allg5.KeyEscape:
 				l.showMenu = true
 				l.menu.Activate(0)
+			case allg5.KeyF5:
+				l.pathFinding = !l.pathFinding
 			}
 			l.state.TryPlayerMove(e.KeyCode)
 		}
@@ -191,19 +195,19 @@ func (l *playLevel) Render(ctx *alui.Context, bounds geom.RectangleF32) {
 		}
 	}
 
-	for i, t := range level.tiles {
+	for i, t := range level.Tiles {
-		pos := geom.Pt(i%level.width, i/level.width)
+		pos := geom.Pt(i%level.Width, i/level.Width)
 		scr := entityLoc{pos.ToF32(), 0}
 		switch t {
-		case tileBasic:
+		case soko.TileTypeBasic:
 			if l.state.IsNextToMagma(pos) {
 				l.drawSprite("lava_brick", "magma", scr)
 			} else {
 				l.drawSprite("lava_brick", "lava_brick", scr)
 			}
-		case tileMagma:
+		case soko.TileTypeMagma:
 			l.drawSprite("magma", "magma", scr)
-			brick := l.state.FindSunkenBrick(pos)
+			brick := l.state.FindSunkenBrickEntity(pos)
 			if brick != nil {
 				behind, front := splitParticles(scr.pos.Y, l.state.Particles(pos))
 				drawParticles(behind)
@@ -214,26 +218,30 @@ func (l *playLevel) Render(ctx *alui.Context, bounds geom.RectangleF32) {
 		}
 	}
 
-	entities := l.state.Entities()
+	entities := l.state.Entities().RenderOrder()
-	sort.Slice(entities, func(i, j int) bool {
-		if entities[i].scr.pos.Y == entities[j].scr.pos.Y {
-			return entities[i].scr.pos.X < entities[j].scr.pos.X
-		}
-		return entities[i].scr.pos.Y < entities[j].scr.pos.Y
-	})
-
 	for _, e := range entities {
 		switch e.typ {
-		case entityTypeBrick:
+		case soko.EntityTypeBrick:
 			l.drawSprite("brick", "brick", e.scr)
-		case entityTypeCharacter:
+		case soko.EntityTypePlayer:
 			l.drawSprite("dragon", "dragon", e.scr)
-		case entityTypeEgg:
+		case soko.EntityTypeTarget:
 			l.drawSprite("egg", "egg", e.scr)
 		}
 	}
 
 	font := ctx.Fonts.Get("default")
+
+	if l.pathFinding {
+		dists := soko.NewPathFinder(&l.state.state).FindDistances()
+		for i := range level.Tiles {
+			pos := geom.Pt(i%level.Width, i/level.Width)
+			scr := entityLoc{pos.ToF32(), 0}
+			posDist := l.posToScreenF32(scr.pos, -20)
+			ctx.Fonts.DrawAlignFont(font, posDist.X, posDist.Y, posDist.X, ctx.Palette.Text, allg5.AlignCenter, strconv.Itoa(dists[i]))
+		}
+	}
+
 	steps := fmt.Sprintf("STEPS: %d", l.state.Steps())
 	ctx.Fonts.DrawAlignFont(font, bounds.Min.X, 24, bounds.Max.X, ctx.Palette.Text, allg5.AlignCenter, steps)
 

cmd/krampus19/playlevelstate.go

@@ -7,17 +7,19 @@ import (
 	"opslag.de/schobers/allg5"
 	"opslag.de/schobers/geom"
 	"opslag.de/schobers/krampus19/gut"
+	"opslag.de/schobers/krampus19/soko"
 )
 
 type playLevelState struct {
 	ctx *Context
 
 	pack   levelPack
-	level  level
+	level  soko.Level
+	state  soko.State
 	player *entity
 	egg    *entity
-	bricks entityList
+	bricks entityMap
-	sunken entityList
+	sunken entityMap
 	splash map[geom.Point]*splashAnimation
 
 	steps      int
@@ -29,9 +31,14 @@ type playLevelState struct {
 	keysDown keyPressedState
 }
 
-func (s *playLevelState) Entities() entityList {
+func (s *playLevelState) Entities() entityMap {
-	var entities entityList
+	entities := entityMap{}
-	return entities.Add(s.player).Add(s.egg).AddList(s.bricks)
+	entities[s.player.id] = s.player
+	entities[s.egg.id] = s.egg
+	for id, e := range s.bricks {
+		entities[id] = e
+	}
+	return entities
 }
 
 func (s *playLevelState) Particles(at geom.Point) []particle {
@@ -48,39 +55,48 @@ func (s *playLevelState) Particles(at geom.Point) []particle {
 	return particles
 }
 
-func (s *playLevelState) FindSunkenBrick(pos geom.Point) *entity {
+func (s *playLevelState) FindSunkenBrickEntity(pos geom.Point) *entity {
-	return s.sunken.FindEntity(pos)
+	idx := s.level.PosToIdx(pos)
+	if idx == -1 {
+		return nil
+	}
+	id := s.state.SunkenBricks[idx]
+	if id != -1 {
+		return s.sunken[id]
+	}
+	return nil
 }
 
 func (s *playLevelState) IsNextToMagma(pos geom.Point) bool {
-	return s.checkTile(pos.Add2D(1, 0), s.isMagma) ||
+	return s.state.Any(soko.IsMagma, soko.Neighbours(pos)...)
-		s.checkTile(pos.Add2D(-1, 0), s.isMagma) ||
-		s.checkTile(pos.Add2D(0, -1), s.isMagma) ||
-		s.checkTile(pos.Add2D(0, 1), s.isMagma)
 }
 
 func (s *playLevelState) Init(ctx *Context, pack, level string, onComplete func()) {
 	s.ctx = ctx
 	s.pack = ctx.Levels.ByID(pack)
 	s.level = s.pack.levels[level]
+	s.state = s.level.State()
 	s.bricks = nil
 	s.sunken = nil
 	s.splash = map[geom.Point]*splashAnimation{}
-	for i, e := range s.level.entities {
+
-		switch e {
+	newEntity := func(e soko.Entity) *entity { return newEntity(e, s.state.IdxToPos[e.Pos]) }
-		case entityTypeBrick:
+
-			s.bricks = append(s.bricks, newEntity(e, s.level.idxToPos(i)))
+	s.player = newEntity(s.state.Player)
-		case entityTypeCharacter:
+	s.egg = newEntity(s.state.Target)
-			s.player = newEntity(e, s.level.idxToPos(i))
+	s.bricks = entityMap{}
-		case entityTypeEgg:
+	for _, e := range s.state.Entities {
-			s.egg = newEntity(e, s.level.idxToPos(i))
+		if e.Typ != soko.EntityTypeBrick {
+			continue
 		}
+		s.bricks[e.ID] = newEntity(soko.Entity{ID: e.ID, Pos: e.Pos, Typ: soko.EntityTypeBrick})
 	}
+	s.sunken = entityMap{}
 	s.keysDown = keyPressedState{}
 	s.onComplete = onComplete
 }
 
-func (s *playLevelState) Level() level { return s.level }
+func (s *playLevelState) Level() soko.Level { return s.level }
 
 func (s *playLevelState) PressKey(key allg5.Key) {
 	s.keysDown[key] = true
@@ -97,58 +113,64 @@ func (s *playLevelState) Tick(now time.Duration) {
 }
 
 func (s *playLevelState) TryPlayerMove(key allg5.Key) {
-	var dir geom.Point
+	var dir soko.Direction
 	switch key {
 	case s.ctx.Settings.Controls.MoveUp:
-		dir = geom.Pt(0, -1)
+		dir = soko.DirectionUp
 	case s.ctx.Settings.Controls.MoveRight:
-		dir = geom.Pt(1, 0)
+		dir = soko.DirectionRight
 	case s.ctx.Settings.Controls.MoveDown:
-		dir = geom.Pt(0, 1)
+		dir = soko.DirectionDown
 	case s.ctx.Settings.Controls.MoveLeft:
-		dir = geom.Pt(-1, 0)
+		dir = soko.DirectionLeft
 	default:
 		return
 	}
-	s.tryPlayerMove(dir, key)
+	s.tryPlayerMove(dir)
 }
 
-func (s *playLevelState) tryPlayerMove(dir geom.Point, key allg5.Key) {
+func (s *playLevelState) tryPlayerMove(dir soko.Direction) {
-	if s.player.scr.pos != s.player.pos.ToF32() {
+	playerPt := s.state.IdxToPos[s.state.Player.Pos]
+	if s.player.scr.pos != playerPt.ToF32() {
 		return
 	}
 
-	to := s.player.pos.Add(dir)
+	state, ok := s.state.MovePlayer(dir)
-	if !s.canMove(s.player.pos, dir) {
+	if !ok {
-		log.Printf("Move is not allowed (tried out move to %s after key '%s' was pressed)", to, gut.KeyToString(key))
+		log.Printf("Move is not allowed (tried out move %s)", dir.String())
 		return
 	}
 
-	if brick := s.bricks.FindEntity(to); brick != nil {
+	to := state.Player.Pos
-		log.Printf("Pushing brick at %s", to)
+	toPt := state.IdxToPos[to]
-		brickTo := to.Add(dir)
+
-		s.ani.StartFn(s.ctx.Tick, newMoveAnimation(brick, brickTo), func() {
+	if brickID := s.state.Bricks[to]; brickID != -1 {
+		log.Printf("Brick %d moved", brickID)
+		brick := s.bricks[brickID]
+		brickTo := state.Entities.ByID(brickID).Pos
+		brickToPt := state.IdxToPos[brickTo]
+		s.ani.StartFn(s.ctx.Tick, newMoveAnimation(brick, toPt, brickToPt), func() {
 			log.Printf("Brick movement finished")
-			if s.checkTile(brickTo, s.wouldBrickSink) {
+			if sunkenBrickID := state.SunkenBricks[brickTo]; sunkenBrickID == brickID {
-				log.Printf("Sinking brick at %s", brickTo)
+				log.Printf("Sinking brick %d", brickID)
-				s.bricks = s.bricks.Remove(brickTo)
+				delete(s.bricks, brickID)
-				s.sunken = s.sunken.Add(brick)
+				s.sunken[brickID] = brick
 				s.ani.Start(s.ctx.Tick, newSinkAnimation(brick))
 
-				splash := newSplashAnimation(brickTo)
+				splash := newSplashAnimation(brickToPt)
-				s.splash[brickTo] = splash
+				s.splash[brickToPt] = splash
 				s.ani.StartFn(s.ctx.Tick, splash, func() {
-					delete(s.splash, brickTo)
+					delete(s.splash, brickToPt)
 				})
 			}
 		})
 	}
 
 	s.steps++
-	log.Printf("Moving player to %s", to)
+	log.Printf("Moving player to %s", toPt)
-	s.ani.StartFn(s.ctx.Tick, newMoveAnimation(s.player, to), func() {
+	s.ani.StartFn(s.ctx.Tick, newMoveAnimation(s.player, playerPt, toPt), func() {
 		log.Printf("Player movement finished")
-		if s.player.pos == s.egg.pos {
+		if to == state.Target.Pos {
 			s.complete = true
 			if onComplete := s.onComplete; onComplete != nil {
 				onComplete()
@@ -156,74 +178,11 @@ func (s *playLevelState) tryPlayerMove(dir geom.Point, key allg5.Key) {
 		} else {
 			pressed := s.keysDown.ArePressed(s.ctx.Settings.Controls.MovementKeys()...)
 			if len(pressed) == 1 {
+				key := pressed[0]
 				log.Printf("Movement key %s is down, moving further", gut.KeyToString(key))
-				s.TryPlayerMove(pressed[0])
+				s.TryPlayerMove(key)
 			}
 		}
 	})
-}
+	s.state = state
-
-func (s *playLevelState) canMove(from, dir geom.Point) bool {
-	to := from.Add(dir)
-	if !s.checkTile(to, s.isSolidTile) {
-		return false
-	}
-	brick := s.bricks.FindEntity(to)
-	if brick != nil {
-		brickTo := to.Add(dir)
-		return !s.checkTileNotFound(brickTo, s.isObstructed, true)
-	}
-	return true
-}
-
-func (s *playLevelState) checkTile(pos geom.Point, check func(pos geom.Point, idx int, t tile) bool) bool {
-	return s.checkTileNotFound(pos, check, false)
-}
-
-func (s *playLevelState) checkTileNotFound(pos geom.Point, check func(pos geom.Point, idx int, t tile) bool, notFound bool) bool {
-	idx := s.level.posToIdx(pos)
-	if idx == -1 {
-		return notFound
-	}
-	return check(pos, idx, s.level.tiles[idx])
-}
-
-func (s *playLevelState) findEntityAt(pos geom.Point) *entity {
-	if s.player.pos == pos {
-		return s.player
-	}
-	brick := s.bricks.FindEntity(pos)
-	if brick != nil {
-		return brick
-	}
-	return s.sunken.FindEntity(pos)
-}
-
-func (s *playLevelState) isObstructed(pos geom.Point, idx int, t tile) bool {
-	if s.bricks.FindEntity(pos) != nil {
-		return true // brick
-	}
-	switch s.level.tiles[idx] {
-	case tileMagma:
-		return false
-	case tileBasic:
-		return false
-	}
-	return true
-}
-
-func (s *playLevelState) isMagma(pos geom.Point, idx int, t tile) bool { return t == tileMagma }
-
-func (s *playLevelState) isSolidTile(pos geom.Point, idx int, t tile) bool {
-	switch t {
-	case tileBasic:
-		return true
-	case tileMagma:
-		return s.sunken.FindEntity(pos) != nil
-	}
-	return false
-}
-
-func (s *playLevelState) wouldBrickSink(pos geom.Point, idx int, t tile) bool {
-	return t == tileMagma && s.sunken.FindEntity(pos) == nil
 }

cmd/krampus19/sprite.go

@@ -7,6 +7,7 @@ import (
 	"strings"
 
 	"opslag.de/schobers/geom"
+	"opslag.de/schobers/krampus19/gut"
 )
 
 type sprite struct {
@@ -33,7 +34,7 @@ type spritePart struct {
 func loadSpriteAsset(r io.Reader) (sprite, error) {
 	var l sprite
 	ctx := spriteContext{&l, nil}
-	err := parseLines(r, ctx.parse)
+	err := gut.ParseLines(r, ctx.parse)
 	if err != nil {
 		return sprite{}, err
 	}
@@ -45,44 +46,44 @@ type spriteContext struct {
 	part   *spritePart
 }
 
-func (c *spriteContext) parse(p *lineParser) parseLineFn {
+func (c *spriteContext) parse(p *gut.LineParser) gut.ParseLineFn {
-	if p.skipSpaceEOF() {
+	if p.SkipSpaceEOF() {
 		return nil
 	}
-	line := p.peek()
+	line := p.Peek()
 	switch {
 	case strings.HasPrefix(line, "sprite:"):
-		p.next()
+		p.Next()
 		return c.parseContent
 	default:
 		return nil
 	}
 }
 
-func (c *spriteContext) parseContent(p *lineParser) parseLineFn {
+func (c *spriteContext) parseContent(p *gut.LineParser) gut.ParseLineFn {
 	const partTag = "part:"
 	const textureTag = "texture:"
 	const spriteEndTag = ":sprite"
-	if p.skipSpaceEOF() {
+	if p.SkipSpaceEOF() {
-		return p.emitErr(errUnexpectedEnd)
+		return p.EmitErr(gut.ErrUnexpectedEnd)
 	}
-	line := p.peek()
+	line := p.Peek()
 	switch {
 	case strings.HasPrefix(line, textureTag):
 		c.sprite.texture = strings.TrimSpace(line[len(textureTag):])
-		p.next()
+		p.Next()
 		return c.parseContent
 	case line == partTag:
-		p.next()
+		p.Next()
 		c.part = &spritePart{}
 		return c.parsePart
 	case line == spriteEndTag:
 		return nil
 	}
-	return p.emitErr(errors.New("unexpected content of sprite"))
+	return p.EmitErr(errors.New("unexpected content of sprite"))
 }
 
-func (c *spriteContext) parsePart(p *lineParser) parseLineFn {
+func (c *spriteContext) parsePart(p *gut.LineParser) gut.ParseLineFn {
 	mustAtois := func(s ...string) []int {
 		res := make([]int, len(s))
 		var err error
@@ -110,14 +111,14 @@ func (c *spriteContext) parsePart(p *lineParser) parseLineFn {
 	const anchorTag = "anchor:"
 	const scaleTag = "scale:"
 	const partEndTag = ":part"
-	if p.skipSpaceEOF() {
+	if p.SkipSpaceEOF() {
-		return p.emitErr(errUnexpectedEnd)
+		return p.EmitErr(gut.ErrUnexpectedEnd)
 	}
-	line := p.peek()
+	line := p.Peek()
 	switch {
 	case strings.HasPrefix(line, nameTag):
 		c.part.name = strings.TrimSpace(line[len(nameTag):])
-		p.next()
+		p.Next()
 		return c.parsePart
 	case strings.HasPrefix(line, subTextureTag):
 		var coords = mustCoords(line[len(subTextureTag):])
@@ -125,7 +126,7 @@ func (c *spriteContext) parsePart(p *lineParser) parseLineFn {
 			panic("expected four coordinates (min x, min y, size x, size y)")
 		}
 		c.part.sub = geom.Rect(coords[0], coords[1], coords[0]+coords[2], coords[1]+coords[3])
-		p.next()
+		p.Next()
 		return c.parsePart
 	case strings.HasPrefix(line, anchorTag):
 		var coords = mustCoords(line[len(anchorTag):])
@@ -133,16 +134,16 @@ func (c *spriteContext) parsePart(p *lineParser) parseLineFn {
 			panic("expected two coordinates (min x, min y)")
 		}
 		c.part.anchor = geom.Pt(coords[0], coords[1])
-		p.next()
+		p.Next()
 		return c.parsePart
 	case strings.HasPrefix(line, scaleTag):
 		c.part.scale = mustAtof(line[len(scaleTag):])
-		p.next()
+		p.Next()
 		return c.parsePart
 	case line == partEndTag:
 		c.sprite.parts = append(c.sprite.parts, *c.part)
-		p.next()
+		p.Next()
 		return c.parseContent
 	}
-	return p.emitErr(errors.New("unexpected content of part"))
+	return p.EmitErr(errors.New("unexpected content of part"))
 }

gut/lineparser.go

@@ -0,0 +1,66 @@
+package gut
+
+import (
+	"errors"
+	"io"
+	"io/ioutil"
+	"strings"
+)
+
+type LineParser struct {
+	lines []string
+	i     int
+	err   error
+}
+
+var ErrUnexpectedEnd = errors.New("unexpected end of file")
+
+func (p *LineParser) EOF() bool { return p.i == len(p.lines) }
+
+func (p *LineParser) EmitErr(err error) ParseLineFn {
+	p.err = err
+	return nil
+}
+
+func (p *LineParser) Next() string {
+	i := p.i
+	p.i++
+	return p.lines[i]
+}
+
+func (p *LineParser) Peek() string { return p.lines[p.i] }
+
+func (p *LineParser) SkipSpaceEOF() bool {
+	for !p.EOF() && len(strings.TrimSpace(p.Peek())) == 0 {
+		p.Next()
+	}
+	return p.EOF()
+}
+
+func SkipSpaceBeforeContent(next ParseLineFn) ParseLineFn {
+	return func(p *LineParser) ParseLineFn {
+		if p.SkipSpaceEOF() {
+			return p.EmitErr(ErrUnexpectedEnd)
+		}
+		return next
+	}
+}
+
+type ParseLineFn func(p *LineParser) ParseLineFn
+
+func ParseLines(r io.Reader, fn ParseLineFn) error {
+	content, err := ioutil.ReadAll(r)
+	if err != nil {
+		return err
+	}
+	lines := strings.Split(string(content), "\n")
+	for i, line := range lines {
+		lines[i] = strings.TrimRight(line, "\r\n")
+	}
+
+	parser := &LineParser{lines: lines}
+	for fn != nil {
+		fn = fn(parser)
+	}
+	return parser.err
+}

soko/direction.go

@@ -0,0 +1,64 @@
+package soko
+
+import "opslag.de/schobers/geom"
+
+type Direction int
+
+const (
+	DirectionUp Direction = iota
+	DirectionRight
+	DirectionDown
+	DirectionLeft
+)
+
+var Directions = [4]Direction{DirectionUp, DirectionRight, DirectionDown, DirectionLeft}
+
+func (d Direction) Invert() Direction {
+	switch d {
+	case DirectionUp:
+		return DirectionDown
+	case DirectionRight:
+		return DirectionLeft
+	case DirectionDown:
+		return DirectionUp
+	case DirectionLeft:
+		return DirectionRight
+	}
+	panic("invalid direction")
+}
+
+func (d Direction) String() string {
+	switch d {
+	case DirectionUp:
+		return "up"
+	case DirectionRight:
+		return "right"
+	case DirectionDown:
+		return "down"
+	case DirectionLeft:
+		return "left"
+	}
+	return "invalid"
+}
+
+func (d Direction) ToPoint() geom.Point {
+	switch d {
+	case DirectionUp:
+		return geom.Pt(0, -1)
+	case DirectionRight:
+		return geom.Pt(1, 0)
+	case DirectionDown:
+		return geom.Pt(0, 1)
+	case DirectionLeft:
+		return geom.Pt(-1, 0)
+	}
+	return geom.Point{}
+}
+
+func Neighbours(p geom.Point) []geom.Point {
+	neighbours := make([]geom.Point, 4)
+	for i, dir := range Directions {
+		neighbours[i] = p.Add(dir.ToPoint())
+	}
+	return neighbours
+}

soko/entity.go

@@ -0,0 +1,48 @@
+package soko
+
+type Entity struct {
+	ID  int
+	Pos int
+	Typ EntityType
+}
+
+type Entities []Entity
+
+func (e Entities) ByID(id int) Entity {
+	idx := e.IdxById(id)
+	if idx == -1 {
+		return Entity{ID: -1}
+	}
+	return e[idx]
+}
+
+func (e Entities) Clone() Entities {
+	clone := make(Entities, len(e))
+	copy(clone, e)
+	return clone
+}
+
+func (e Entities) IdxById(id int) int {
+	for i, e := range e {
+		if e.ID == id {
+			return i
+		}
+	}
+	return -1
+}
+
+type Ints []int
+
+func NewInts(n int) Ints {
+	ids := make(Ints, n)
+	for i := range ids {
+		ids[i] = -1
+	}
+	return ids
+}
+
+func (e Ints) Clone() Ints {
+	clone := make(Ints, len(e))
+	copy(clone, e)
+	return clone
+}

soko/entitylocations.go

@@ -0,0 +1,31 @@
+package soko
+
+import "opslag.de/schobers/geom"
+
+type EntityLocations map[geom.Point]int
+
+func (l EntityLocations) Add(p geom.Point, id int) { l[p] = id }
+
+func (l EntityLocations) Clone() EntityLocations {
+	clone := EntityLocations{}
+	for p, id := range l {
+		clone[p] = id
+	}
+	return clone
+}
+
+func (l EntityLocations) Has(p geom.Point) bool {
+	_, ok := l[p]
+	return ok
+}
+
+func (l EntityLocations) Move(from, to geom.Point) {
+	id, ok := l[from]
+	if !ok {
+		panic("no entitiy at position")
+	}
+	l.Remove(from)
+	l.Add(to, id)
+}
+
+func (l EntityLocations) Remove(p geom.Point) { delete(l, p) }

soko/entitytype.go

@@ -0,0 +1,23 @@
+package soko
+
+type EntityType byte
+
+const (
+	EntityTypeInvalid EntityType = EntityType(0)
+	EntityTypeNone               = '_'
+	EntityTypePlayer             = '@'
+	EntityTypeTarget             = 'X'
+	EntityTypeBrick              = 'B'
+)
+
+func (e EntityType) IsValid() bool {
+	switch e {
+	case EntityTypeNone:
+	case EntityTypePlayer:
+	case EntityTypeTarget:
+	case EntityTypeBrick:
+	default:
+		return false
+	}
+	return true
+}

soko/level.go

@@ -0,0 +1,91 @@
+package soko
+
+import (
+	"opslag.de/schobers/geom"
+)
+
+type Level struct {
+	Width  int
+	Height int
+
+	Tiles    []TileType
+	Entities []EntityType
+}
+
+func (l Level) IdxToPos(i int) geom.Point { return geom.Pt(i%l.Width, i/l.Width) }
+
+func (l Level) PosToIdx(p geom.Point) int {
+	if p.X < 0 || p.Y < 0 || p.X >= l.Width || p.Y >= l.Height {
+		return -1
+	}
+	return p.Y*l.Width + p.X
+}
+
+func (l Level) Moves() []Moves {
+	moves := make([]Moves, len(l.Tiles))
+	w := l.Width
+	for y := 0; y < l.Height; y++ {
+		for x := 0; x < w; x++ {
+			var m Moves
+			idx := y*w + x
+			if y > 0 {
+				m.Valid = append(m.Valid, idx-w)
+				m.All[DirectionUp] = idx - w
+			} else {
+				m.All[DirectionUp] = -1
+			}
+			if y < (l.Height - 1) {
+				m.Valid = append(m.Valid, idx+w)
+				m.All[DirectionDown] = idx + w
+			} else {
+				m.All[DirectionDown] = -1
+			}
+			if x > 0 {
+				m.Valid = append(m.Valid, idx-1)
+				m.All[DirectionLeft] = idx - 1
+			} else {
+				m.All[DirectionLeft] = idx - 1
+			}
+			if x < (w - 1) {
+				m.Valid = append(m.Valid, idx+1)
+				m.All[DirectionRight] = idx + 1
+			} else {
+				m.All[DirectionRight] = idx + 1
+			}
+			moves[idx] = m
+		}
+	}
+	return moves
+}
+
+func (l Level) MoveIdx(idx int, dir Direction) int {
+	switch dir {
+	case DirectionUp:
+		if idx < l.Width {
+			return -1
+		}
+		return idx - l.Width
+	case DirectionRight:
+		if (idx+1)%l.Width == 0 {
+			return -1
+		}
+		return idx + 1
+	case DirectionDown:
+		if idx >= (l.Width*l.Height)-l.Width {
+			return -1
+		}
+		return idx + l.Width
+	case DirectionLeft:
+		if idx%l.Width == 0 {
+			return -1
+		}
+		return idx - 1
+	}
+	return -1
+}
+
+func (l Level) Size() int { return l.Width * l.Height }
+
+func (l Level) State() State {
+	return NewState(l)
+}

soko/levelparser.go

@@ -0,0 +1,85 @@
+package soko
+
+import (
+	"errors"
+	"fmt"
+	"io"
+
+	"opslag.de/schobers/krampus19/gut"
+)
+
+func ParseLevel(r io.Reader) (Level, error) {
+	var l Level
+	ctx := levelContext{&l}
+	err := gut.ParseLines(r, ctx.parse)
+	if err != nil {
+		return Level{}, err
+	}
+	return l, nil
+}
+
+type levelContext struct {
+	level *Level
+}
+
+func (c *levelContext) parse(p *gut.LineParser) gut.ParseLineFn {
+	if p.EOF() {
+		return nil
+	}
+	switch p.Peek() {
+	case "level:":
+		return c.parseContent
+	case "":
+		p.Next() // skip
+		return c.parse
+	default:
+		return nil
+	}
+}
+
+func (c *levelContext) parseContent(p *gut.LineParser) gut.ParseLineFn {
+	if p.Next() != "level:" {
+		return p.EmitErr(errors.New("expected level start"))
+	}
+	return c.parseRow
+}
+
+func (c *levelContext) parseRow(p *gut.LineParser) gut.ParseLineFn {
+	if p.EOF() {
+		return p.EmitErr(errors.New("unexpected end of file"))
+	}
+	line := p.Next()
+	if line == ":level" {
+		return c.parse
+	}
+	if c.level.Height == 0 {
+		c.level.Width = len(line) / 2
+	}
+	return c.addRow(p, line)
+}
+
+func (c *levelContext) addRow(p *gut.LineParser, line string) gut.ParseLineFn {
+	var tiles []TileType
+	var entities []EntityType
+	for i := 0; i < len(line); i += 2 {
+		tiles = append(tiles, TileType(line[i]))
+		entities = append(entities, EntityType(line[i+1]))
+	}
+
+	for i, t := range tiles {
+		if !t.IsValid() {
+			return p.EmitErr(fmt.Errorf("level contains invalid TileType at (%d, %d)", i, c.level.Height))
+		}
+	}
+	for i, e := range entities {
+		if !e.IsValid() {
+			return p.EmitErr(fmt.Errorf("level contains invalid entity type at (%d, %d)", i, c.level.Height))
+		}
+	}
+
+	c.level.Height++
+	c.level.Tiles = append(c.level.Tiles, tiles...)
+	c.level.Entities = append(c.level.Entities, entities...)
+
+	return c.parseRow
+}

soko/locations.go

@@ -0,0 +1,17 @@
+package soko
+
+import "opslag.de/schobers/geom"
+
+type Locations map[geom.Point]bool
+
+func (l Locations) Add(p geom.Point) { l[p] = true }
+
+func (l Locations) Clone() Locations {
+	clone := Locations{}
+	for p := range l {
+		clone[p] = true
+	}
+	return clone
+}
+
+func (l Locations) Remove(p geom.Point) { delete(l, p) }

soko/moves.go

@@ -0,0 +1,6 @@
+package soko
+
+type Moves struct {
+	All   [4]int
+	Valid []int
+}

soko/pathfinder.go

@@ -0,0 +1,133 @@
+package soko
+
+import (
+	"sort"
+)
+
+type PathFinder struct {
+	state *State
+	moves []Moves
+}
+
+func NewPathFinder(s *State) PathFinder {
+	return PathFinder{s, nil}
+}
+
+func NewPathFinderMoves(s *State, moves []Moves) PathFinder {
+	return PathFinder{s, moves}
+}
+
+func (p PathFinder) Find(target int) []int {
+	source := p.state.Player.Pos
+	level := p.state.Level
+	size := level.Size()
+	distances := NewInts(size)
+	distances[source] = 0
+	moves := NewInts(size)
+	moves[source] = source
+	state := p.newPathFinderState(source)
+
+	heuristic := func(i int) int {
+		idx := state.frontier[i]
+		return distances[idx] + p.state.IdxToPos[idx].DistInt(p.state.IdxToPos[target])
+	}
+	for {
+		curr := state.frontier[0]
+		if curr == target {
+			break
+		}
+		state.frontier = state.frontier[1:]
+
+		state.findBetterNeighbours(distances, curr, func(nextIdx, newDistance int) {
+			moves[nextIdx] = curr
+		})
+
+		if len(state.frontier) == 0 {
+			return nil // no path
+		}
+
+		// apply heuristic to frontier (favor points closer to target)
+		sort.Slice(state.frontier, func(i, j int) bool { return heuristic(i) < heuristic(j) })
+	}
+
+	// build reverse path
+	curr := target
+	path := []int{curr}
+	for {
+		curr = moves[curr]
+		if curr == source {
+			break
+		}
+		path = append(path, curr)
+	}
+	// reverse path
+	n := len(path)
+	for i := 0; i < n/2; i++ {
+		path[i], path[n-i-1] = path[n-i-1], path[i]
+	}
+	return path
+}
+
+func (p PathFinder) FindDistances() Ints {
+	source := p.state.Player.Pos
+	level := p.state.Level
+	size := level.Size()
+	distances := NewInts(size)
+	distances[source] = 0
+	state := p.newPathFinderState(source)
+
+	for {
+		curr := state.frontier[0]
+		state.frontier = state.frontier[1:]
+
+		state.findBetterNeighbours(distances, curr, nil)
+
+		if len(state.frontier) == 0 {
+			return distances
+		}
+	}
+}
+
+func (p PathFinder) newPathFinderState(source int) *pathFinderState {
+	return &pathFinderState{p.state, append(make([]int, 0, p.state.Level.Size()), source), p.moves}
+}
+
+type pathFinderState struct {
+	state    *State
+	frontier []int
+	moves    []Moves
+}
+
+type betterNeighbourFn func(int, int)
+
+func (s *pathFinderState) findBetterNeighbours(distances []int, curr int, better betterNeighbourFn) {
+	currDistance := distances[curr]
+	newDistance := currDistance + 1
+
+	var moves []int
+	if s.moves == nil {
+		for _, dir := range Directions {
+			nextIdx := s.state.Level.MoveIdx(curr, dir)
+			if nextIdx == -1 {
+				continue
+			}
+			moves = append(moves, nextIdx)
+		}
+	} else {
+		moves = s.moves[curr].Valid
+	}
+	for _, nextIdx := range moves {
+		if distance := distances[nextIdx]; distance != -1 && distance <= newDistance { // skip when shorter path exists
+			continue
+		}
+		if !s.state.Walkable[nextIdx] || s.state.Bricks[nextIdx] != -1 { // filter neighbours
+			continue
+		}
+		distances[nextIdx] = newDistance
+		s.frontier = append(s.frontier, nextIdx)
+		if better == nil {
+			continue
+		}
+		better(nextIdx, newDistance)
+	}
+}

soko/solver.go

@@ -0,0 +1,94 @@
+package soko
+
+func Solve(l Level) int {
+	state := l.State()
+	return solve(state)
+}
+
+func solve(state State) int {
+	level := state.Level
+	target := state.Target.Pos
+	costs := &stateCostQueue{}
+	costs.Put(&stateCost{&state, 0, nil})
+	costsByPlayerIdx := make([][]*stateCost, level.Size())
+	findCost := func(s *State) *stateCost {
+		costs := costsByPlayerIdx[s.Player.Pos]
+		for i := 0; i < len(costs); i++ {
+			if !costs[i].state.Equal(s) {
+				continue
+			}
+			return costs[i]
+		}
+		return nil
+	}
+	addCost := func(next *State, nextCost int) {
+		cost := findCost(next)
+		if cost == nil {
+			newCost := &stateCost{next, nextCost, nil}
+			costs.Put(newCost)
+			player := next.Player.Pos
+			costsByPlayerIdx[player] = append(costsByPlayerIdx[player], newCost)
+		} else if nextCost < cost.cost {
+			cost.cost = nextCost
+			costs.Update(cost)
+		}
+	}
+	moves := level.Moves()
+	type direction struct {
+		dir     Direction
+		inverse Direction
+	}
+	dirs := make([]direction, 4)
+	for _, dir := range Directions {
+		dirs[dir] = direction{dir, dir.Invert()}
+	}
+	for {
+		curr := costs.Get()
+		currPlayerPos := curr.state.Player.Pos
+		if currPlayerPos == target {
+			return curr.cost
+		}
+
+		if curr.distances == nil {
+			curr.distances = NewPathFinderMoves(curr.state, moves).FindDistances()
+		}
+		distances := curr.distances
+		for _, e := range curr.state.Entities {
+			idx := e.Pos
+			if e.Typ != EntityTypeBrick || curr.state.SunkenBricks[idx] == e.ID {
+				continue
+			}
+			for i := 0; i < 4; i++ {
+				player := moves[e.Pos].All[dirs[i].inverse]
+				if player == -1 {
+					continue
+				}
+				walk := distances[player]
+				if walk == -1 {
+					continue
+				}
+				if !curr.state.IsOpenForBrick(curr.state.IdxToPos[moves[e.Pos].All[i]]) {
+					continue
+				}
+				curr.state.Player.Pos = player
+				next, ok := curr.state.MovePlayer(dirs[i].dir)
+				if !ok {
+					panic("should be a valid move")
+				}
+				nextCost := curr.cost + walk + 1
+				addCost(&next, nextCost)
+			}
+		}
+		curr.state.Player.Pos = currPlayerPos
+		if walk := distances[target]; walk != -1 {
+			next := curr.state.Clone()
+			next.Player.Pos = target
+			nextCost := curr.cost + walk
+			addCost(&next, nextCost)
+		}
+
+		if costs.Empty() {
+			return -1
+		}
+	}
+}

soko/solver_test.go

@@ -0,0 +1,111 @@
+package soko
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+var levelBenchmark = `level:
+._._._._._._._._._._._._._._._._._._._._
+._._._._._#_#_#_._._._._._._._._._._._._
+._._._._._#_#_#_._._._._._._._._._._._._
+._._._._._#_#_#_._._._._._._._._._._._._
+._._._#_#_#_#_#_#_._._._._._._._._._._._
+._._._#_._#_._._#_._._._._#X#_#_~_#_#_._
+._#_#_#_._#_._._#_._._._._._._._~_#_#_._
+._#_#B#_#_#B#_#_#_#_#_#_#_#_#_#_#_#_#_._
+._._._._._#_._._._#_._#@._._._._#_#_._._
+._._._._._#_#_#_#_#_._._._._._._._._._._
+._._._._._._._._._._._._._._._._._._._._
+:level`
+
+var levelEasy = `level:
+._._._._._._._._._._
+._#@#_#_#B#_~_#_#X._
+._._._._._._._._._._
+:level`
+
+var level1 = `level:
+._._._._._._._._._._
+._#_#_#_#_~_~_~_#_._
+._#_#_._#B~_~_#_#_._
+._#_#_#_#_~_~_~_#_._
+._#_#_._#B~_~_#_#_._
+._#@#_#_#_~_~_#_#X._
+._#_#_~_~_~_#_#_#_._
+._#_#_~_~_~_#_#_#_._
+._._._._._._._._._._
+:level`
+
+var level2 = `level:
+._._._._._._._._._._._._._._._._._._._._
+._._._._._#_#_#_._._._._._._._._._._._._
+._._._._._#B#_#_._._._._._._._._._._._._
+._._._._._#_#_#B._._._._._._._._._._._._
+._._._#_#_#B#_#B#_._._._._._._._._._._._
+._._._#_._#_._._#_._._._._#X#_~_~_~_#_._
+._#_#_#_._#_._._#_._._._._._._._~_~_#_._
+._#_#B#_#_#B#_#_#_#_#_#_#_#_#_#_~_#_#_._
+._._._._._#_._._._#_._#@._._._._#_#_._._
+._._._._._#_#_#_#_#_._._._._._._._._._._
+._._._._._._._._._._._._._._._._._._._._
+:level`
+
+var level3 = `level:
+._._._._._._._._._._
+._._._._._._._._._._
+._~_#_#_#_#B#_._._._
+._~_#B#_#_._#_._._._
+._~_._#_~_#_#_._._._
+._#X._#_~_#_._._._._
+._._#_#B#_#_._._._._
+._._#@#_._._._._._._
+._._._._._._._._._._
+:level`
+
+var level4 = `level:
+._._._._._._._._._._._._
+._._#_#_._._._._._._._._
+._._#_#B#_#B#@#_#_._._._
+._._#_#_#_#_#B#_#_._._._
+._._._._._._#_._._._._._
+._._._._._._#_._._._._._
+._._._._._._#B._._._._._
+._._._#_#_._#_._#_#_._._
+._#_#_#_#_~_#_#_#_#_#_._
+._#_._._#_._#_._#_._#_._
+._#_._#X~_._~_._~_._#_._
+._#_._._#_._#_._#_._#_._
+._#_#_#_#_#_~_#_#_#_#_._
+._._._._._._._._._._._._
+:level`
+
+func mustParseLevel(s string) Level {
+	l, err := ParseLevel(bytes.NewBufferString(s))
+	if err != nil {
+		panic("couldn't parse level")
+	}
+	return l
+}
+
+func TestSolver(t *testing.T) {
+	solve := func(s string) int {
+		l := mustParseLevel(s)
+		steps := Solve(l)
+		return steps
+	}
+	assert.Equal(t, 7, solve(levelEasy))
+	assert.Equal(t, 35, solve(level1))
+	// assert.Equal(t, -1, solve(level2))
+	assert.Equal(t, 49, solve(level3))
+	// assert.Equal(t, -1, solve(level4))
+}
+
+func BenchmarkSolver(b *testing.B) {
+	l := mustParseLevel(levelBenchmark)
+	for n := 0; n < b.N; n++ {
+		Solve(l)
+	}
+}

soko/state.go

@@ -0,0 +1,240 @@
+package soko
+
+import "opslag.de/schobers/geom"
+
+type State struct {
+	Player Entity
+	Target Entity
+
+	Entities Entities
+
+	Level        Level
+	IdxToPos     []geom.Point
+	Bricks       Ints
+	SunkenBricks Ints
+	Walkable     []bool
+
+	nextEntityID int
+}
+
+func NewState(l Level) State {
+	size := l.Size()
+	s := State{
+		Entities:     Entities{},
+		Level:        l,
+		IdxToPos:     make([]geom.Point, size),
+		Bricks:       NewInts(size),
+		SunkenBricks: NewInts(size),
+		Walkable:     make([]bool, size),
+	}
+
+	for idx, t := range l.Tiles {
+		switch t {
+		case TileTypeBasic:
+			s.Walkable[idx] = true
+		}
+		s.IdxToPos[idx] = s.Level.IdxToPos(idx)
+	}
+
+	for idx, e := range l.Entities {
+		pos := s.IdxToPos[idx]
+		switch e {
+		case EntityTypeBrick:
+			s.addBrick(pos)
+		case EntityTypePlayer:
+			s.initPlayer(pos)
+		case EntityTypeTarget:
+			s.initTarget(pos)
+		}
+	}
+	return s
+}
+
+// Clone creates and returns a clone of the state.
+func (s State) Clone() State {
+	return State{
+		Player:       s.Player,
+		Target:       s.Target,
+		Entities:     s.Entities.Clone(),
+		Level:        s.Level,
+		IdxToPos:     s.IdxToPos,
+		Bricks:       s.Bricks.Clone(),
+		SunkenBricks: s.SunkenBricks.Clone(),
+		Walkable:     append(s.Walkable[:0:0], s.Walkable...),
+		nextEntityID: s.nextEntityID,
+	}
+}
+
+func (s State) All(pred func(State, geom.Point) bool, p ...geom.Point) bool {
+	for _, p := range p {
+		if !pred(s, p) {
+			return false
+		}
+	}
+	return true
+}
+
+func (s State) Any(pred func(State, geom.Point) bool, p ...geom.Point) bool {
+	for _, p := range p {
+		if pred(s, p) {
+			return true
+		}
+	}
+	return false
+}
+
+func (s *State) Equal(other *State) bool {
+	for i := 0; i < len(s.Entities); i++ {
+		if other.Entities[i].Pos != s.Entities[i].Pos {
+			return false
+		}
+	}
+	return true
+}
+
+func (s State) IsOpenForBrick(p geom.Point) bool {
+	idx := s.Level.PosToIdx(p)
+	if idx == -1 {
+		return false
+	}
+	return s.isOpenForBrick(idx)
+}
+
+// IsWalkable indicates that a player could walk over this tile regardless of any Bricks that might be there.
+func (s State) IsWalkable(p geom.Point) bool {
+	idx := s.Level.PosToIdx(p)
+	if idx == -1 {
+		return false
+	}
+	return s.Walkable[idx]
+}
+
+// IsWalkableAndFree indicates that a player can walk over this tile (no brick is at the tile).
+func (s State) IsWalkableAndFree(p geom.Point) bool {
+	idx := s.Level.PosToIdx(p)
+	if idx == -1 {
+		return false
+	}
+	return s.Walkable[idx] && s.Bricks[idx] == -1
+}
+
+// MovePlayer tries to move the player in the specified direction. Returns the new state and true if the move is valid. Returns the current state and false is the move was invalid.
+func (s State) MovePlayer(dir Direction) (State, bool) {
+	to := s.Level.MoveIdx(s.Player.Pos, dir)
+	if to == -1 {
+		return s, false
+	}
+
+	if !s.Walkable[to] {
+		return s, false
+	}
+
+	brickID := s.Bricks[to]
+	if brickID == -1 {
+		return s.Mutate(func(s *State) {
+			s.movePlayer(to)
+		}), true
+	}
+
+	brickTo := s.Level.MoveIdx(to, dir)
+	if brickTo == -1 {
+		return s, false
+	}
+	if !s.isOpenForBrick(brickTo) {
+		return s, false
+	}
+	return s.Mutate(func(s *State) {
+		s.movePlayer(to)
+
+		if s.Level.Tiles[brickTo] == TileTypeMagma && s.SunkenBricks[brickTo] == -1 {
+			s.SunkenBricks[brickTo] = brickID
+			s.Walkable[brickTo] = true
+			s.Bricks[to] = -1
+		} else {
+			s.Bricks[brickTo] = brickID
+			s.Bricks[to] = -1
+		}
+		s.updateEntity(brickID, Entity{brickID, brickTo, EntityTypeBrick})
+	}), true
+}
+
+func (s State) SetPlayer(to geom.Point) (State, bool) {
+	toIdx := s.Level.PosToIdx(to)
+	if toIdx == -1 {
+		return s, false
+	}
+	if !s.Walkable[toIdx] {
+		return s, false
+	}
+	if s.Bricks[toIdx] != -1 {
+		return s, false
+	}
+	return s.Mutate(func(s *State) {
+		s.movePlayer(toIdx)
+	}), true
+
+}
+
+// Mutate clones the state, applies the mutation on the clone and returns the clone.
+func (s State) Mutate(fn func(s *State)) State {
+	clone := s.Clone()
+	fn(&clone)
+	return clone
+}
+
+func (s *State) addBrick(pos geom.Point) {
+	s.addEntity(pos, EntityTypeBrick, func(e Entity) {
+		idx := s.Level.PosToIdx(pos)
+		if idx != -1 {
+			s.Bricks[idx] = e.ID
+		}
+	})
+}
+
+func (s *State) addEntity(pos geom.Point, typ EntityType, add func(Entity)) {
+	id := s.nextEntityID
+	e := Entity{id, s.Level.PosToIdx(pos), typ}
+	add(e)
+	s.Entities = append(s.Entities, e)
+	s.nextEntityID++
+}
+
+func (s *State) initPlayer(pos geom.Point) {
+	s.addEntity(pos, EntityTypePlayer, func(e Entity) {
+		s.Player = e
+	})
+}
+
+func (s *State) initTarget(pos geom.Point) {
+	s.addEntity(pos, EntityTypeTarget, func(e Entity) {
+		s.Target = e
+	})
+}
+
+func (s State) isOpenForBrick(idx int) bool {
+	if s.Walkable[idx] {
+		return s.Bricks[idx] == -1
+	}
+	return s.Level.Tiles[idx] == TileTypeMagma
+}
+
+func (s *State) updateEntity(id int, e Entity) {
+	idx := s.Entities.IdxById(id)
+	if idx == -1 {
+		return
+	}
+	s.Entities[idx] = e
+}
+
+func (s *State) movePlayer(to int) {
+	s.Player.Pos = to
+	s.updateEntity(s.Player.ID, Entity{s.Player.ID, to, EntityTypePlayer})
+}
+
+func IsMagma(s State, p geom.Point) bool {
+	idx := s.Level.PosToIdx(p)
+	if idx == -1 {
+		return false
+	}
+	return s.Level.Tiles[idx] == TileTypeMagma
+}

soko/statecost.go

@@ -0,0 +1,71 @@
+package soko
+
+type stateCost struct {
+	state     *State
+	cost      int
+	distances Ints
+}
+
+type stateCostQueue struct {
+	first *stateCostQueueItem
+}
+
+type stateCostQueueItem struct {
+	Value *stateCost
+	Next  *stateCostQueueItem
+}
+
+func (q *stateCostQueue) Empty() bool {
+	return q.first == nil
+}
+
+func (q *stateCostQueue) Get() *stateCost {
+	if q.Empty() {
+		panic("nothing in queue")
+	}
+	first := q.first
+	q.first = first.Next
+	return first.Value
+}
+
+func (q *stateCostQueue) Put(value *stateCost) {
+	priority := value.cost
+	item := &stateCostQueueItem{value, nil}
+	if q.Empty() {
+		q.first = item
+		return
+	}
+	if priority < q.first.Value.cost {
+		item.Next = q.first
+		q.first = item
+		return
+	}
+	curr := q.first
+	for curr.Next != nil {
+		if priority < curr.Next.Value.cost {
+			item.Next = curr.Next
+			curr.Next = item
+			return
+		}
+		curr = curr.Next
+	}
+	curr.Next = item
+}
+
+func (q *stateCostQueue) Update(value *stateCost) {
+	var prev *stateCostQueueItem
+	curr := q.first
+	for curr.Value != value {
+		prev = curr
+		curr = curr.Next
+		if curr == nil {
+			panic("not in queue")
+		}
+	}
+	if prev == nil {
+		q.first = curr.Next
+	} else {
+		prev.Next = curr.Next
+	}
+	q.Put(value)
+}

soko/tiletype.go

@@ -0,0 +1,21 @@
+package soko
+
+type TileType byte
+
+const (
+	TileTypeInvalid TileType = TileType(0)
+	TileTypeNothing          = '.'
+	TileTypeBasic            = '#'
+	TileTypeMagma            = '~'
+)
+
+func (t TileType) IsValid() bool {
+	switch t {
+	case TileTypeNothing:
+	case TileTypeBasic:
+	case TileTypeMagma:
+	default:
+		return false
+	}
+	return true
+}