新背景：Tunnel

parts/backgrounds/tunnel.lua

@@ -0,0 +1,43 @@
+--Cool Tunnel
+local gc=love.graphics
+local rnd=math.random
+local ins,rem=table.insert,table.remove
+local back={}
+
+local ring
+local t
+local W,H
+function back.init()
+	ring={}
+	t=26
+	back.resize(SCR.w,SCR.h)
+end
+function back.resize(w,h)
+	W,H=w,h
+end
+function back.update(dt)
+	t=t-1
+	if t==0 then
+		t=rnd(26,62)
+		ins(ring,0)
+	end
+	for i=#ring,1,-1 do
+		ring[i]=ring[i]+dt
+		if ring[i]>3.55 then
+			rem(ring,i)
+		end
+	end
+end
+function back.draw()
+	gc.clear(.1,.1,.1)
+	gc.setColor(.4,.4,.4)
+	for i=1,#ring do
+		local r=ring[i]^2/12
+		gc.setLineWidth(30-15/(r+.5))
+		gc.rectangle("line",640-W*r/2,360-H*r/2,W*r,H*r)
+	end
+end
+function back.discard()
+	ring=nil
+end
+return back