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/welcome.lua

@@ -0,0 +1,39 @@
+--Welcome to Techmino
+local gc=love.graphics
+local rnd,sin=math.random,math.sin
+local back={}
+
+local t
+local txt
+function back.init()
+	t=rnd()*2600
+	txt=gc.newText(getFont(80),"Welcome To Techmino")
+end
+function back.update(dt)
+	t=t+dt
+end
+function back.draw()
+	if -t%13.55<.1283 then
+		gc.clear(.2+.1*sin(t),.2+.1*sin(1.26*t),.2+.1*sin(1.626*t))
+	else
+		gc.clear(.1,.1,.1)
+	end
+	gc.push("transform")
+	gc.replaceTransform(xOy)
+	gc.translate(640,360)
+	gc.scale(1.1626,1.26)
+	if -t%6.26<.1355 then
+		gc.translate(60*sin(t*.26),100*sin(t*.626))
+	end
+	if -t%12.6<.1626 then
+		gc.rotate(t+5*sin(.26*t)+5*sin(.626*t))
+	end
+	gc.setColor(.2,.3,.5)
+	gc.draw(txt,-883*.5+4*sin(t*.7942),-110*.5+4*sin(t*.7355))
+	gc.setColor(.4,.6,.8)
+	gc.draw(txt,-883*.5+2*sin(t*.77023),-110*.5+2*sin(t*.7026))
+	gc.setColor(.9,.9,.9)
+	gc.draw(txt,-883*.5+3*sin(t*.7283),-110*.5+3*sin(t*.7626))
+	gc.pop()
+end
+return back