Personally I thought the art was pretty cute (says the guy that used pixel art lol). I did notice the difficulty increase slightly after a score of 45 (maybe the RNG decided to give me more ships?) but I think a gradual increase in difficulty would have made it much better. The cannon cooldown time hardly even mattered as well. I stopped after reaching a score of 100. I can see this being an interesting mobile game if you expanded and refined the game more :)