diff --git a/snowdogs.p8 b/snowdogs.p8
index 5671d6a..c0d5b20 100644
--- a/snowdogs.p8
+++ b/snowdogs.p8
@@ -14,8 +14,8 @@ function _update()
 	if mode == "title" then
 		update_title()
 	elseif mode == "game" then
-		handle_input()
-		update_trees()
+		sled_upd()
+		trees_upd()
 	end
 end
 
@@ -25,10 +25,9 @@ function _draw()
 		draw_snow()
 	elseif mode == "game" then
 		draw_game()
-		draw_snow()
-		--pdebug()
-		draw_collide()
-		draw_hud()
+		--draw_snow()
+		--draw_hud()
+		--draw_bounds()
 	end
 end
 
@@ -37,11 +36,51 @@ function draw_game()
 	cls(6)
 	-- grey transparency
 	palt(0b000001000000000)
-	draw_trees()
-	draw_dogs()
+	trees_dr()
+	sled_dr()
 	palt()
 end
 
+-->8
+-- title
+title_y = 0
+title_stretch = 0
+title_rainbow = 0
+title_susan = -40
+title_89 = 40
+
+function update_title()
+	if title_y < 50 then
+		title_y += 1
+	elseif title_stretch < 16 then
+		title_stretch += 1
+	end 
+	if title_stretch == 16 and title_susan < 30 then
+		title_susan += 1
+		title_89 -= 1
+	end
+	
+	if btnp(4) then
+		mode = "game"
+	end
+end
+
+function draw_title()
+	cls(0)
+	
+	if title_susan then
+		print("susan butcher's", title_susan, title_susan + 10, 12)
+	end
+	
+	pal(8, 8+t()%6)
+	pal(12, 8+(t()+4)%6)
+	sspr(48, 24, 54, 16,
+	 40-title_stretch, title_y,
+	 54+title_stretch*2, 16+title_stretch)
+	sspr(104, 24, 16, 16,
+	 70+title_89, 100+title_89,
+	 48, 48)
+end	
 -->8
 -- snow
 
@@ -78,61 +117,8 @@ end
 -->8
 -- game entities
 
-function draw_dogs()
-	local d = {[0]=5, 6, 5, 7, 7, 6}
-	for x=0,1 do
-		for y=0,2 do
-			local dx = 64 - (10 * x) +
-				 									(steering*4*y)
-			if y*2+x < dogs then
-				spr(d[y*2+x], dx,
-					128-(16*(y+1)), 1, 2)
-			end
-		end
-	end
-end
-
-function draw_tree(x, y)
-	spr(11, x, y, 1, 2)
-end
-
-function draw_trees()
-	for i=1,8 do
-		draw_tree(
-			left_wall[i]-8 - sled_x + 64,
-			(i-1)*16
-		)
-		draw_tree(
-			right_wall[i] - sled_x + 64,
-			(i-1)*16
-		)
-	end
-end
-
-function tree_spread()
-	-- ret: 2 vals, 15 to 60
-	-- width of field
-	local diff = 15+((goal - distance) / goal)*45
-	shift = rnd(60-diff)*rnd({-1, 1})
-	diff += rnd(diff*0.2)-diff*0.1
-	return left_wall[1]+shift, left_wall[1]+shift+diff
-end
-
-function update_trees()
-	local new_dist = distance + speed
-	if flr(new_dist / 16) > flr(distance / 16) then
-		-- shift 'em down
-		for i = 8,2,-1 do
-			left_wall[i] = left_wall[i-1]
-			right_wall[i] = right_wall[i-1]
-		end
-		-- new tree at back
-		
-		l, r = tree_spread()
-		left_wall[1] = l
-		right_wall[1] = r
-	end
-end
+goal = 10000
+mode = "title"
 
 function draw_hud()
 	rectfill(14,0,114,4,7)
@@ -143,7 +129,7 @@ function draw_hud()
 		print("🐱", 1, (l-1)*7, 7)
 	end
 	print("▒", 108, 0, 0)
-	
+
 	if distance >= goal then
 		print("you win!", 35, 64)
 	-- if distance is near 100
@@ -151,32 +137,25 @@ function draw_hud()
 		local mtg = ceil((goal-distance)/1000)*100
 		print(mtg.." miles to go!", 30, 64)
 	end
-	
 end
--->8
--- global state
 
-goal = 10000
-mode = "title"
+function draw_bounds()
+	sl, sr = sled_bounds()
+	rect(screenx(sl), 128-16*3, screenx(sr), 128)
+	tl, tr = tree_bounds()
+	rect(screenx(tl), 100, screenx(tr), 128)
+end 
+-->8
+-- sled
+
 steering = 0
 speed = 1
 distance = 0 -- 10ths of mile
 sled_x = 64
 dogs = 6
 
-left_wall = {
-	22, 20, 20, 18, 
-	18, 16, 16, 16,
-}
 
-right_wall = {
-	112, 112, 114, 114,
-	116, 118, 118, 118
-}
-
--->8
--- update logic
-function handle_input()
+function sled_upd()
 	if btn(0) then
 		steering = -1
 	elseif btn(1) then
@@ -184,19 +163,22 @@ function handle_input()
 	else
 		steering = 0
 	end
+
+	speed = 1 + (distance / 3000)
 	
-	if btn(2) then
-		speed = 20
-	else
-		speed = 1
+	if btnp(4) then
+		speed *= 3
+		--steering = rnd({-2, 2})
 	end
 	
 	distance += speed
 	sled_x += steering * speed
 	
-	l, r = bounds()
-	if sled_x-5 < l or sled_x+5 > r then
-				crash()
+	sl, sr = sled_bounds()
+	tl, tr = tree_bounds()
+	--printh(tl.." "..sl..","..sr.." "..tr)
+	if sl < tl or sr > tr then
+		crash()
 	end
 	
 	if distance >= goal then
@@ -204,77 +186,119 @@ function handle_input()
 	end
 end
 
-function bounds()
-	-- return left, right
-	w = {8, 8, 7, 7, 6, 6}
-	w = w[dogs]
-	return left_wall[w],
-		right_wall[w]
+function sled_bounds()
+	if dogs % 2 == 0 then
+		return sled_x-8, sled_x+8
+	else
+		return sled_x, sled_x+8
+	end
 end
 
-function draw_collide()
-	rect(52, 108, 72, 128)
-	l, r = bounds()
- line(l, 90, l, 128, 3)
- line(r, 90, r, 128, 3)
-end
-
-
 function crash()
 	sfx(4)
 	dogs -= 1
 	if dogs == 0 then
 		mode = "gameover"
 	end
-	sled_x = (left_wall[8]+right_wall[8])/2
+	sled_x = tree_wall[8].l + tree_wall[8].w / 2
 end
 
+function sled_dr()
+	local d = {[0]=5, 6, 5, 7, 7, 6}
+	for x=0,1 do
+		for y=0,2 do
+			if y*2+x < dogs then
+				-- draw dogs centered
+				local dx = screenx(sled_x + steering*4*y) + (8 * (x-1))
+				spr(d[y*2+x], dx, 128-(16*(y+1)), 1, 2)
+			end
+		end
+	end
+end
+
+
 -->8
--- title
+-- trees
 
-title_y = 0
-title_stretch = 0
-title_rainbow = 0
-title_susan = -40
-title_89 = 40
+-- left & width
+tree_wall = {
+	{l=5, w=80}, 
+	{l=5, w=80},
+	{l=5, w=80},
+	{l=5, w=80},
+	{l=10, w=80},
+	{l=15, w=80},
+	{l=20, w=80},
+	{l=17, w=80},
+	{l=23, w=80},
+	{l=25, w=80},
+} -- 1..10
 
-function update_title()
-	if title_y < 50 then
-		title_y += 1
-	elseif title_stretch < 16 then
-		title_stretch += 1
-	end 
-	if title_stretch == 16 and title_susan < 30 then
-		title_susan += 1
-		title_89 -= 1
-	end
-	
-	if btnp(4) then
-		mode = "game"
+function draw_tree(x, y)
+	spr(11, x, y, 1, 2)
+end
+
+function screenx(x)
+	-- world x to screen x
+	return x + 64 - sled_x
+end
+
+function cur_tree()
+	-- 
+	return #tree_wall - flr((distance / 16) % #tree_wall)
+end
+
+function trees_dr()
+	local ct=cur_tree()
+	for i=-2,8 do
+		tree = tree_wall[(ct+i) % #tree_wall + 1]
+		draw_tree(
+			screenx(tree.l),
+			i*16 + (distance % 16)
+		)
+		draw_tree(
+			screenx(tree.l + tree.w),
+			i*16 + (distance % 16)
+		)
 	end
 end
 
-function draw_title()
-	cls(0)
-	
-	if title_susan then
-		print("susan butcher's",
-		title_susan,
-		title_susan + 10, 12)
+function trees_upd()
+	local new_dist = distance + speed
+	if flr(new_dist / 16) > flr(distance / 16) then
+		add_next_tree()
 	end
-	
-	pal(8, 8+t()%6)
-	pal(12, 8+(t()+4)%6)
-	sspr(48, 24, 54, 16,
-				  40-title_stretch,
-				  title_y,
-				  54+title_stretch*2,
-				  16+title_stretch)
-	sspr(104, 24, 16, 16,
-						70+title_89,
-						100+title_89,
-						48, 48)
-end	
+end
+
+function add_next_tree()
+	local pct = (goal - distance) / goal
+	-- TODO: adjust difficulty
+	local minw = 70 + 45 * pct
+	local maxw = 90 - 50 * pct
+	local nw = tree_wall[1].w + rnd(8)-4
+	local idx = cur_tree() - 1
+	if idx == 0 then
+		idx = #tree_wall
+	end
+
+	tree_wall[idx] = 
+ 	{
+		l=tree_wall[cur_tree()].l + rnd(8)-4 + steering,
+		w=max(min(nw, maxw), minw)
+	}
+end
+
+function tree_bounds()
+	-- return left, right
+	-- use wall based on dogs
+	-- remaining
+	w = {8, 8, 7, 7, 6, 6}
+	w = w[dogs]
+	l = tree_wall[w].l
+	-- middle of tree is bound
+	return l+8, l+tree_wall[w].w+8
+end
+
 __gfx__
 00000000644444466444444667c7c7c6666666666666666666666666666666660000000000033000666666666666666600000000666666666666666600000000
 000000006499994664999946c777777c666666666666666666666666556666550000000000033000666336666663766600000000466666646666666600000000