Just watched the stream, you were supposed to shoot at the red squares that would shoot back at you and the challenge was mirroring your bullets to shoot enemies that go behind you but the spawning system was broken. I admit it was horrible (being my first project in that engine). I agree with a lot of the points you made but this game is just something I made for the jam and I don't plan on going back even to fix it. Thanks for the feedback!
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The thing is you know the keys to press to achieve this since you coded the game but we don't.
You can easily address that by editing the description of your game (this isn't locked during the voting period) and provide some clarify on this for the benefits of the players who will try it next.
As for this being your first project in that engine, everybody starts somewhere so don't beat yourself up and keep going!