diff --git a/game/commands.go b/game/commands.go
index df470aa..b195d0e 100644
--- a/game/commands.go
+++ b/game/commands.go
@@ -13,7 +13,7 @@ const (
 	right
 )
 
-func doCommand(cmd command, s State, teamID int) State {
+func doCommand(cmd command, s State, sOld State, teamID int) State {
 	da := 1
 	da += rand.Intn(3) - 1
 
@@ -35,5 +35,5 @@ func doCommand(cmd command, s State, teamID int) State {
 		b.Lane--
 	}
 
-	return updateBot(s, teamID, *b)
+	return updateBot(s, sOld, teamID, *b)
 }
diff --git a/game/game.go b/game/game.go
index dfc7417..100a190 100644
--- a/game/game.go
+++ b/game/game.go
@@ -1,8 +1,98 @@
 package game
 
-import (
-	"log"
-)
+func UpdateState(s State, sOld State) State {
+	for i := range s.Teams {
+		s = doCommand(chooseCommand(s, i), s, sOld, i)
+		if b := activeBot(s.Teams[i]); b != nil {
+			s = moveBot(s, i, *b)
+		}
+		s = maybePassBaton(s, i)
+	}
+
+	for _, t := range s.Teams {
+		if b := activeBot(t); b != nil && won(*b, s) {
+			s.GameOver = true
+		}
+	}
+
+	return s
+}
+
+func maybePassBaton(s State, teamID int) State {
+	t := s.Teams[teamID]
+	h := activeBot(t)
+	if h == nil {
+		return s
+	}
+
+	for i, b := range t.Bots {
+		if h.ID >= b.ID || h.Lane != b.Lane {
+			continue
+		}
+		if abs(b.Pos-h.Pos) <= passDistance {
+			h.v = 0
+			h.a = 0
+			s = updateBot(s, s, teamID, *h)
+			newH := t.Bots[i]
+			newH.a = baseAccel
+			t.Baton.HolderID = newH.ID
+			s = updateTeam(s, t)
+			return updateBot(s, s, teamID, newH)
+		}
+	}
+
+	return s
+}
+
+func activeBot(t Team) *Bot {
+	for _, b := range t.Bots {
+		if b.ID == t.Baton.HolderID {
+			return &b
+		}
+	}
+	return nil
+}
+
+func updateBot(s State, sOld State, teamID int, b Bot) State {
+	t := s.Teams[teamID]
+	for i, bb := range t.Bots {
+		if bb.ID == b.ID {
+			bots := append([]Bot{}, t.Bots[:i]...)
+			bots = append(bots, b)
+			bots = append(bots, t.Bots[i+1:]...)
+			t.Bots = bots
+			break
+		}
+	}
+
+	s = updateTeam(s, t)
+	return s
+}
+
+func updateTeam(s State, t Team) State {
+	s.Teams = append(s.Teams[:t.id], append([]Team{t}, s.Teams[t.id+1:]...)...)
+	return s
+}
+
+func won(b Bot, s State) bool {
+	return b.Pos >= Steps
+}
+
+func gameOver(s State) bool {
+	for _, t := range s.Teams {
+		if t.won {
+			return true
+		}
+	}
+	return false
+}
+
+func abs(n int) int {
+	if n < 0 {
+		return -n
+	}
+	return n
+}
 
 type State struct {
 	Teams     []Team
@@ -10,6 +100,40 @@ type State struct {
 	GameOver  bool
 }
 
+type Team struct {
+	id    int
+	Bots  []Bot
+	Baton Baton
+	won   bool
+	Lane  int
+}
+
+func (t Team) BatonHolder() *Bot {
+	for _, b := range t.Bots {
+		if b.ID == t.Baton.HolderID {
+			return &b
+		}
+	}
+	return nil
+}
+
+type Bot struct {
+	ID   int
+	Lane int
+	Pos  int
+	v    int
+	a    int
+}
+
+type Baton struct {
+	HolderID int
+}
+
+type Obstacle struct {
+	Lane int
+	Pos  int
+}
+
 func NewState() State {
 	var teams []Team
 	for i := 0; i < NumTeams; i++ {
@@ -53,124 +177,6 @@ func NewState() State {
 	}
 }
 
-type Team struct {
-	id    int
-	Bots  []Bot
-	Baton Baton
-	won   bool
-	Lane  int
-}
-
-func (t Team) BatonHolder() *Bot {
-	for _, b := range t.Bots {
-		if b.ID == t.Baton.HolderID {
-			return &b
-		}
-	}
-	return nil
-}
-
-type Bot struct {
-	ID   int
-	Lane int
-	Pos  int
-	v    int
-	a    int
-}
-
-type Baton struct {
-	HolderID int
-}
-
-type Obstacle struct {
-	Lane int
-	Pos  int
-}
-
-func UpdateState(s State) State {
-	for i, t := range s.Teams {
-		s = doCommand(chooseCommand(s, i), s, i)
-		if b := activeBot(t); b != nil {
-			s = moveBot(s, i, *b)
-		}
-		s = maybePassBaton(s, i)
-	}
-
-	for _, t := range s.Teams {
-		if b := activeBot(t); b != nil && won(*b, s) {
-			s.GameOver = true
-		}
-	}
-
-	return s
-}
-
-func maybePassBaton(s State, teamID int) State {
-	t := s.Teams[teamID]
-	h := activeBot(t)
-	if h == nil {
-		return s
-	}
-
-	for i, b := range t.Bots {
-		if h.ID >= b.ID || h.Lane != b.Lane {
-			continue
-		}
-		if abs(b.Pos-h.Pos) <= passDistance {
-			log.Printf("team %v pass from %v to %v!", teamID, h.ID, b.ID)
-			h.v = 0
-			h.a = 0
-			s = updateBot(s, teamID, *h)
-			newH := t.Bots[i]
-			newH.a = baseAccel
-			t.Baton.HolderID = newH.ID
-			s = updateTeam(s, t)
-			return updateBot(s, teamID, newH)
-		}
-	}
-
-	return s
-}
-
-func activeBot(t Team) *Bot {
-	for _, b := range t.Bots {
-		if b.ID == t.Baton.HolderID {
-			return &b
-		}
-	}
-	return nil
-}
-
-func updateBot(s State, teamID int, b Bot) State {
-	t := s.Teams[teamID]
-	for i, bb := range t.Bots {
-		if bb.ID == b.ID {
-			t.Bots = append(t.Bots[:i], append([]Bot{b}, t.Bots[i+1:]...)...)
-			break
-		}
-	}
-
-	return updateTeam(s, t)
-}
-
-func updateTeam(s State, t Team) State {
-	s.Teams = append(s.Teams[:t.id], append([]Team{t}, s.Teams[t.id+1:]...)...)
-	return s
-}
-
-func won(b Bot, s State) bool {
-	return b.Pos >= Steps
-}
-
-func gameOver(s State) bool {
-	for _, t := range s.Teams {
-		if t.won {
-			return true
-		}
-	}
-	return false
-}
-
 const (
 	Steps    = 50
 	numBots  = 5
@@ -179,10 +185,3 @@ const (
 	maxA     = 3
 	maxV     = 10
 )
-
-func abs(n int) int {
-	if n < 0 {
-		return -n
-	}
-	return n
-}
diff --git a/game/physics.go b/game/physics.go
index 2f1478d..ed6da9d 100644
--- a/game/physics.go
+++ b/game/physics.go
@@ -26,7 +26,8 @@ func moveBot(s State, teamID int, b Bot) State {
 		}
 	}
 
-	return updateBot(s, teamID, b)
+	s = updateBot(s, s, teamID, b)
+	return s
 }
 
 func collide(pos, lane int, s State) bool {
diff --git a/gfx/gfx.go b/gfx/gfx.go
index 998defd..886cab4 100644
--- a/gfx/gfx.go
+++ b/gfx/gfx.go
@@ -17,32 +17,50 @@ type RenderState struct {
 	frame     int
 }
 
-func Render(rs RenderState, s game.State, w *pixelgl.Window, d time.Duration) RenderState {
-	//tween := float64(rs.frame) / float64(rs.Frames)
+func Render(rs RenderState, sOld, sNew game.State, w *pixelgl.Window, d time.Duration) RenderState {
+	//log.Println("render")
+	w.Clear(colornames.Peru)
 
-	colors := teamColors(s.Teams)
-	renderBots(s, w, d, colors)
-	renderObstacles(s, w)
+	tween := float64(rs.frame) / float64(rs.Frames)
+
+	colors := teamColors(sNew.Teams)
+	renderBots(sOld, sNew, tween, w, d, colors)
+	renderObstacles(sNew, w)
 
 	rs.frame++
+	//log.Println("frame", rs.frame)
 	if rs.frame >= rs.Frames {
 		rs.Animating = false
 	}
 	return rs
 }
 
-func renderBots(s game.State, w *pixelgl.Window, d time.Duration, colors map[*game.Team]pixel.RGBA) {
+func renderBots(sOld, sNew game.State, tween float64, w *pixelgl.Window, d time.Duration, colors map[*game.Team]pixel.RGBA) {
 	bounds := w.Bounds()
 	im := imdraw.New(nil)
 
-	for i, t := range s.Teams {
+	//log.Println("sOld.Teams:", sOld.Teams)
+
+	for i, t := range sNew.Teams {
 		for j, bot := range t.Bots {
-			c := colors[&s.Teams[i]]
+			c := colors[&sNew.Teams[i]]
 			c.R += 0.2 * float64(j)
 			c.G -= 0.1 * float64(j)
 			im.Color = c
 
-			pos := lanePos(bot.Pos, bot.Lane, botWidth, bounds)
+			oldBot := sOld.Teams[i].Bots[j]
+			// log.Println("oldBot:", oldBot)
+			// log.Println("bot:", bot)
+			oldPos := lanePos(oldBot.Pos, oldBot.Lane, botWidth, bounds)
+			newPos := lanePos(bot.Pos, bot.Lane, botWidth, bounds)
+
+			// log.Println("oldPos:", oldPos)
+			// log.Println("newPos:", newPos)
+
+			pos := pixel.Vec{
+				X: oldPos.X + tween*(newPos.X-oldPos.X),
+				Y: oldPos.Y + tween*(newPos.Y-oldPos.Y),
+			}
 
 			im.Push(pos)
 
@@ -53,6 +71,7 @@ func renderBots(s game.State, w *pixelgl.Window, d time.Duration, colors map[*ga
 			if t.Bots[j].ID == t.Baton.HolderID {
 				renderBaton(pos, w)
 			}
+			//log.Println("sOld.Teams[i].Bots[j]:", sOld.Teams[i].Bots[j])
 		}
 	}
 }
diff --git a/main.go b/main.go
index a0ac06f..501fa84 100644
--- a/main.go
+++ b/main.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"log"
 	"math/rand"
 	"relay/game"
 	"relay/gfx"
@@ -29,23 +30,26 @@ func run() {
 
 	start := time.Now()
 
+	w.Clear(colornames.Peachpuff)
 	for !w.Closed() && !s.GameOver {
-		w.Clear(colornames.Peru)
+		sOld := s
 
-		//sOld := s
+		rs := gfx.RenderState{
+			Animating: false,
+			Frames:    3,
+		}
 
 		switch {
 		case w.JustPressed(pixelgl.KeyQ):
 			return
 		case w.JustPressed(pixelgl.KeySpace):
-			s = game.UpdateState(s)
-		}
-		rs := gfx.RenderState{
-			Animating: true,
-			Frames:    10,
+			rs.Animating = true
+			s = game.UpdateState(s, sOld)
 		}
 		for rs.Animating {
-			rs = gfx.Render(rs, s, w, time.Since(start))
+			log.Println("anim loop")
+			rs = gfx.Render(rs, sOld, s, w, time.Since(start))
+			w.Update()
 		}
 		w.Update()
 	}