transparency for grids

painter.py

@@ -53,13 +53,18 @@ class Painter(Widget):
     def draw(self):
         self.canvas.clear()
         with self.canvas:
+            # draw order: particles, then grids, then transparent particles
+
+            for particle in self.particles:
+                particle.draw()
+
             # draw grids
             for particle in self.particles:
                 if particle.grid>0:
                     self.draw_grid(particle.squares[0].pos,particle.grid)
 
             for particle in self.particles:
-                particle.draw()
+                particle.draw(alpha=0.5)
 
     def draw_grid(self,pos,mesh):
         # height offset due to status bar and command prompt

polyomino.py

@@ -18,14 +18,15 @@ class Polyomino():
         self.grid=kwargs.get("grid",0)
 
     # draw function
-    def draw(self):
+    def draw(self,**kwargs):
+        alpha=kwargs.get("alpha",1)
         # set color
         if not self.selected:
-            Color(*self.color)
+            Color(*self.color,alpha)
         else:
             (r,g,b)=self.color
             # darken selected
-            Color(r/2,g/2,b/2)
+            Color(r/2,g/2,b/2,alpha)
 
         for square in self.squares:
             Rectangle(pos=((square.pos.x-0.5)*square.size,(square.pos.y-0.5)*square.size),size=(square.size,square.size))