a version of zot that does not look awful

performance impact is probably not acceptable though

collisiontest.p8

@@ -114,7 +114,7 @@ end
 function _draw()
  cls(0)
 	rect(bx0,by0,bx1,by1,6)
-	zot(lx1,ly1,5,lx1-lx0,ly1-ly0,10,9,8)
+	zot(lx1,ly1,0.75,lx1-lx0,ly1-ly0,10,9,8)
 	--line(lx0,ly0,lx1,ly1,2)
 	local cmin, cmax = collides()
 	if cmin then
@@ -140,19 +140,22 @@ function zot_one(x, y, r, ir, dx, dy, hot, warm)
   line(x0-rx,y0+iry,x-irx,y+ry,warm)
   --line(x0-rx,y0-ry,x+rx,y+ry,warm)
  end
- line(x0,y0,x-rx,y-iry,hot)
- line(x0,y0,x+irx,y-ry,hot)
+ line(x0,y0,x+rx,y-iry,hot)
+ line(x0,y0,x-irx,y+ry,hot)
  --line(x0,y0,x+rx,y+ry,hot)
 end
 
-function zot(x,y,r,dx,dy,hot,warm,cold)
- local x0,y0=x-dx,y-dy
- if (cold) rectfill(x0-r,y0-r,x0+r,y0+r,cold)
- for ir=-r,0 do
-  zot_one(x,y,r,ir,dx,dy,hot,warm)
-  zot_one(x,y,r,-ir,dx,dy,hot,warm)
+function zot(x,y,r,dx,dy,hot,cold)
+ local x0,y0,sdx,sdy=x-dx,y-dy,sgn(dx),sgn(dy)
+ local rx,ry=r*sdx,r*sdy
+ for i=-r,r do
+  line(x0+i*sdx,y0-ry,x+rx,y-i*sdy,cold)
+  line(x0-rx,y0+i*sdy,x-i*sdx,y+ry,cold)
+ end
+ for i=-r,r do
+  line(x0,y0,x+rx,y-i*sdy,hot)
+  line(x0,y0,x-i*sdx,y+ry,hot)
  end
- rectfill(x-r,y-r,x+r,y+r,hot)
 end
 __gfx__
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