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/fan.lua

@@ -0,0 +1,75 @@
+--UUZ's fan
+local gc=love.graphics
+local rnd=math.random
+local max,min,sin=math.max,math.min,math.sin
+local ins,rem=table.insert,table.remove
+local back={}
+
+local t
+local fan,petal
+function back.init()
+	t=rnd(2600)
+	fan=title_fan
+	petal={}
+	BG.resize()
+end
+function back.update()
+	t=t+1
+	if t%10==0 then
+		ins(petal,{
+			x=SCR.w*rnd(),
+			y=0,
+			vy=2+rnd()*2,
+			vx=rnd()*2-.5,
+			rx=4+rnd()*4,
+			ry=4+rnd()*4,
+		})
+	end
+	for i=#petal,1,-1 do
+		local P=petal[i]
+		P.y=P.y+P.vy
+		if P.y>SCR.h then
+			rem(petal,i)
+		else
+			P.x=P.x+P.vx
+			P.vx=P.vx+rnd()*.01
+			P.rx=max(min(P.rx+rnd()-.5,10),2)
+			P.ry=max(min(P.ry+rnd()-.5,10),2)
+		end
+	end
+end
+function back.draw()
+	gc.push("transform")
+	gc.translate(SCR.w/2,SCR.h/2+20*sin(t*.02))
+	gc.scale(SCR.k)
+	gc.clear(.1,.1,.1)
+	gc.setLineWidth(320)
+	gc.setColor(.3,.2,.3)
+	gc.arc("line","open",0,420,500,-.8*3.1416,-.2*3.1416)
+
+	gc.setLineWidth(4)
+	gc.setColor(.7,.5,.65)
+	gc.arc("line","open",0,420,660,-.799*3.1416,-.201*3.1416)
+	gc.arc("line","open",0,420,340,-.808*3.1416,-.192*3.1416)
+	gc.line(-281,224,-530,30.5)
+	gc.line(281,224,530,30.5)
+
+	gc.setLineWidth(6)
+	gc.setColor(.55,.5,.6)
+	for i=1,8 do
+		gc.polygon("line",fan[i])
+	end
+
+	gc.setLineWidth(2)
+	gc.setColor(.6,.3,.5)
+	gc.origin()
+	for i=1,#petal do
+		local P=petal[i]
+		gc.ellipse("fill",P.x,P.y,P.rx,P.ry)
+	end
+	gc.pop()
+end
+function back.discard()
+	petal=nil
+end
+return back