It seems like the coin collection uses the same 1-pixel collision that enemy shots do. Coin collection should be based on the whole ship. Nice game otherwise.
I'd like to be able to go back in a campaign and attempt the harder difficulty level to get the upgraded card. Right now, once you complete normal, you can't go back. Otherwise, great game.
You can replay the entire campaign once it's finished. The first time you complete each encounter on each of the 3 difficulties guarantees you a reward. If you do the same encounter on the same difficulty multiple times, the chances to get the reward go down, but if you do all difficulties you'll get 3 copies (level I, II and III) of each card.
Neat idea about the upgrades. But the ship is much too big for a bullet hell game -- usually it's a 1-pixel target. And balance feels off, there's no way to kill most waves.
Neat idea, weak execution. You should pick which traps go where, and build a strategy around placing traps. Traps should fire automatically. Upgrades, both in-level and between-level, would be nice, but what this game really needs is strategy in placing traps, and less focus on clicking each trap constantly.
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You can replay the entire campaign once it's finished. The first time you complete each encounter on each of the 3 difficulties guarantees you a reward. If you do the same encounter on the same difficulty multiple times, the chances to get the reward go down, but if you do all difficulties you'll get 3 copies (level I, II and III) of each card.