Thanks for trying the game and for the constructive comment!
The lack of checkpoint was intentional, the idea was to create a difficult and punishing game, where levels have to be gained attempt after attempt. But I understand it can get a lil frustrating :)
You are right, the kill system was explained briefly in the tutorial, but the instructions were a lot so I guess it's easy to miss it.
Unluckily we run out of time for the sound, for sure it would have added more.