Thank you for playing and taking the time to comment! I left the ending ambiguous and unexplained and basically it's that you're brother who you're waiting for died on his way back to you so it doesn't matter how long you survive, you die eventually as well, regardless if you made it past the 5 minute countdown or not. But now I realize that it is very confusing at best and unsatisfying and annoying at worst. I'm thinking of adding more context, levels and enemies to expand the game so I'll definitely keep your suggestions in mind. And you're right, I didn't playtest the game much so that really hurt the end result. I'll playtest very early on next time.
As for the bug of the ammo count not resetting to 36 after restarting, that's my fault. I forgot to reset the total ammo global variable after restarts. I caught it and fixed it but it was too late, the submission time had passed.
Anyways, thank you again for taking the time to playand comment!