Had alot of fun playing it. Probably in my top 10 games^^.
Loved how well the level design is.
Was very fun to wander around, dodging bullets.
Also i haven't encountered any issues outside of the lack of checkpoints
My proposition would be of removing the game over screen and just respawn the character at the start of the level. You can also set the number of health to like 1-3 to fit that new change.
(Just personal idea lol).
Good work