Nice work.
Is there going to be something random in the boxes? I think I smashed them all then found a circle that needed something heavy putting on it to open a gate. At that point I couldn't find a broken column either.
I didn't think the health bar was very clear. It was difficult to gauge how much damage I was taking when fighting and how much health I got when I picked one up.
In a later tutorial maybe mention the floating cubes that explode? I thought the first one that I encountered was something to collect. Until it blew up!
I might have missed which button was 'jump'? I got stuck in part of a room with different height 'squares' being attacked from one side and stabbed by something in the dark at the other. Then it restarted from the beginning. I was at least 15 minutes into the game. Maybe it could restart from the beginning of the unfinished room?
But it was fun and I will play more to see if I can get further.
The objects at the start are supposed to be things you collect throughout the beginning of the game. For a few reasons, including the fact that this is a short demo level, I just give them to you at the start. In the final game it won't work like this. Note this is not all the items. There are 3 other types of gun in the level that are not at the beginning, and grenades.