Okay, tried it again and updated my rating.
It feels way better when you know how to shoot.
The bullets were a bit small, and hard to see with the VCR effect, so be careful with that.
The checkpoint mechanic felt pretty weird. Any reason to use this "closest check" rather than classic checkpoints that needs you to touch them ?
And again, take note for your next games, don't try hiding keys from your player, even more when they need them to play.
But hey, when you know the controls, your game gets kinda good, so nice work here.