mathematica画区域图遇到填充颜色不满的情况，怎么解决
 

请问一下，以下代码在mathematica中画区域图，为什么会出现填充颜色不满的情况，如下图区域空白地方。
RegionPlot[{(*case1*)1-0.02-x-0.15+0.02>=0&&0.2-0.2x-0.17(1-y)+0.02(x-y)<=0&&0.02-0.2(1-x+y)+0.15<=0&&x>=y,(*case2*)1-0.02-x-0.15+0.02<=0&&x>=y,(*case3*)0.2-0.2x-0.17(1-y)+0.02(x-y)>=0&&x>=y,(*case4*)0.02-0.2(1-x+y)+0.15>=0&&x>=y,(*case5*)1-0.02-x-0.15+0.02<=0&&0.2-0.2x-0.17(1-y)+0.02(x-y)>=0&&x>=y,(*case6*)1-0.02-x-0.15+0.02<=0&&0.02-0.2(1-x+y)+0.15>=0&&x>=y,(*case7*)0.2-0.2x-0.17(1-y)+0.02(x-y)>=0&&0.02-0.2(1-x+y)+0.15>=0&&x>=y},{x,0,1},{x,0,1},FrameStyle->25,PlotRange->{{0,1},{0,1}},FrameLabel->{x,y},PlotStyle->{(*case1*)Lighter[Red,0.4],(*case2*)Lighter[Magenta,0.4],(*case3*)Lighter[Blue,0.4],(*case4*)Lighter[RGBColor[0,255,255],0.2],(*case5*)Lighter[Orange,0.2],(*case6*)Lighter[Green,0.2],(*case7*)Lighter[Purple,0.2]}]
图片参见附件，麻烦各位解答一下