Sergeant nailed it with the feedback about the edge of the screen. Think that a cone of "firing" should be added so the cookie doesn't fire when near edges OR make the game be looped or mirrored (not sure what the term is). Basically if a crumb goes to the right and dissapears from the screen, make it appear on the left. The the mechanic isn't "crumb must not leave the scren".
Actually, thinking about it, think that it would be more entertaining if the players get more points as they shoot smaller crumbs and they slightly grow (due to moister or smtn dunno) and the points decrease with their scale. Then if the crumb gets too large it pops and you lose points.
Another thing is to pause the crumbs when you click on upgrades or blocking the upgrades so the player doesn't look into it while the crumbs are spawning. This is a problem because you are separating the players attention and breaking immersion.
Overall, its a very lovely visually appealing game! Well done and keep it up :)