I played it. It's fun, and I've got a few comments:
1) Don't make Grid walk when he isn't walking (animation-wise).
Good point, thanks. I'll fix it!
2) Grad doesn't seem to stay in the tiles like he's supposed to. He's not drawn in the center of his position.
Well, "supposed to" is subjective
-- I designed the game to let the robot walk freely across the floor, and report the colour he's centred over. On a slightly related note, I do consider it a defect that he can walk half on a wall (since he's not "hitting" the wall until his centre point hits it). Do you think if I fixed this problem that the "not staying centred" problem would bother you less?
The reason I ask is that there are a number of levels (some of my favourites) that depend on the "move freely within squares" setup. I think the game is richer once you get past the expectation that the robot should jump from centre-of-square to centre-of-next-square.
3) There isn't an obvious way to remove accidental connections.
Also a good point. You probably noticed you can do it with Delete, Backspace, and Right-click->remove... but some sort of dragging gesture would be better. Any specific ideas? What was your first instinct?
But, great work!
By the way, which level did you get to?