diff --git a/cart.wren b/cart.wren
index 0b69007..ddced7f 100644
--- a/cart.wren
+++ b/cart.wren
@@ -26,7 +26,7 @@ class Star {
 		TIC.circ(_x, _y, _size, _color)
 	}
 
-	isPassed {
+	expired {
 		_x + _size < 0
 	}
 }
@@ -45,6 +45,10 @@ class Bullet {
 	draw() {
 		TIC.rect(_x, _y, 3, 1, 4)
 	}
+
+	expired {
+		_x > W
+	}
 }
 
 class Ship {
@@ -68,6 +72,8 @@ class Ship {
 		if (TIC.btn(3)) {
 			_x = _x + _speed
 		}
+		_x.clamp(0, W)
+		_y.clamp(0, H)
 
 		if (TIC.btnp(4, 5, 10)) {
 			shoot()
@@ -76,6 +82,9 @@ class Ship {
 		for (b in _bullets) {
 			b.update()
 		}
+		while (_bullets.count > 0 && _bullets[0].expired) {
+			_bullets.removeAt(0)
+		}
 	}
 
 	draw() {
@@ -95,6 +104,9 @@ class World {
 		_t = 0
 		_stars = []
 		_player = Ship.new(W / 2, H / 2)
+		_world_x = 0
+		_world_y = 0
+		_world_scroll_speed = 60 / 2
 
 		// init background
 		for (i in 0..W) {
@@ -109,7 +121,7 @@ class World {
 			s.update()
 		}
 		// collect passed stars
-		while (_stars.count > 0 && _stars[0].isPassed) {
+		while (_stars.count > 0 && _stars[0].expired) {
 			_stars.removeAt(0)
 		}
 		// small stars
@@ -125,9 +137,15 @@ class World {
 			_stars.add(Star.new(W, R.int(0,H), width, speed, 13))
 		}
 		_t = _t + 1
+
+		if (_t % _world_scroll_speed == 0) {
+			_world_x = _world_x + 1
+		}
 	}
 
 	draw() {
+		var sx = (_t % _world_scroll_speed) / (_world_scroll_speed / 8)
+		TIC.map(_world_x, _world_y, 30 + 1, 17 + 1, -sx, 0)
 		for (s in _stars) {
 			s.draw()
 		}
@@ -171,10 +189,13 @@ class Game is TIC{
 // 002:ccccceee8888cceeaaaa0cee888a0ceeccca0ccc0cca0c0c0cca0c0c0cca0c0c
 // 003:eccccccccc888888caaaaaaaca888888cacccccccacccccccacc0ccccacc0ccc
 // 004:ccccceee8888cceeaaaa0cee888a0ceeccca0cccccca0c0c0cca0c0c0cca0c0c
+// 005:2222222223312331231123112111211122222222233123312311231121112111
 // 017:cacccccccaaaaaaacaaacaaacaaaaccccaaaaaaac8888888cc000cccecccccec
 // 018:ccca00ccaaaa0ccecaaa0ceeaaaa0ceeaaaa0cee8888ccee000cceeecccceeee
 // 019:cacccccccaaaaaaacaaacaaacaaaaccccaaaaaaac8888888cc000cccecccccec
 // 020:ccca00ccaaaa0ccecaaa0ceeaaaa0ceeaaaa0cee8888ccee000cceeecccceeee
+// 033:0000000000000000000000000002200000022000000000000000000000000000
+// 034:0000000000000000000000000003300000033000000000000000000000000000
 // </TILES>
 
 // <SPRITES>
@@ -184,6 +205,12 @@ class Game is TIC{
 // 017:ddccccccddddddd0eeeeee000000000000000000000000000000000000000000
 // </SPRITES>
 
+// <MAP>
+// 014:000000000000000000000000000000000000000000000000000000000000000000000000005000000000000000500000000000000050000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+// 015:000000000000000000000000000000000000000000000000000000000000000000000000505050000000000050505000000000005050500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+// 016:000000000000000000000000000000000000000000000000000000000000505050505050505050505050505050505050505050505050505050505050000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+// </MAP>
+
 // <WAVES>
 // 000:00000000ffffffff00000000ffffffff
 // 001:0123456789abcdeffedcba9876543210