重构背景系统（每个背景使用独立文件），全局变量名整理

parts/backgrounds/badapple.lua

@@ -0,0 +1,56 @@
+--Bad Apple!! (128x96, 10fps, 2192f)
+local gc=love.graphics
+local int=math.floor
+local back={}
+
+local bAnd,bRshift=bit.band,bit.rshift
+local t
+local video
+local X,Y,K
+function back.init()
+	if not video then
+		video=love.data.decompress("string","zlib",love.filesystem.read("Zframework/badapple.dat"))
+	end
+	t=0
+	BG.resize()
+end
+function back.resize()
+	local W,H=SCR.w,SCR.h
+	if H/W>=96/128 then
+		K=W/128
+		X,Y=0,(H-W*96/128)*.5
+	else
+		K=H/96
+		X,Y=(W-H*128/96)*.5,0
+	end
+end
+function back.update()
+	t=t+1
+	if t==13146 then
+		t=0
+	end
+end
+function back.draw()
+	gc.clear(.2,.2,.2)
+	gc.push("transform")
+	gc.origin()
+	gc.translate(X,Y)
+	gc.scale(K)
+	gc.setColor(.4,.4,.4)
+	local t1=1536*int(t/6)+1
+	for i=0,1535 do
+		local B=video:byte(t1+i)
+		for j=7,0,-1 do
+			local p=8*i+j
+			if bAnd(B,1)==0 then
+				gc.rectangle("fill",p%128,int(p/128),1,1)
+			end
+			B=bRshift(B,1)
+		end
+	end
+	gc.pop()
+end
+function back.discard()
+	video=nil
+end
+return back