Thanks for playing the game in this state :) I've added better instructions
Bob is trying to finish a painting on his favorite Grid, but the Skull gang is trying to ruin it. Click around Bob to place Colors. Click again to set the destination the Color will move to. Avoid letting the Skulls reach Bob! Colors are like your Bullets (but "Colors" sound more nicer!), they can Kill the Skulls. Try to Place and Aim your Colors well to intercept the Skull's path. Avoid Killing the Little Critters if you can.