Poor balancing prevented me from navigating the game. After some patern learning I managed to pass 1st level.
Upgrades that give a very small amount (+5%) are not exciting. Even tho u can stack them.
You should make it cost more but give more back. Generaly I think this game manipulates numbers too big, make it more intense with a small time (10s) but make bullets free. The game will still be resource management but more intense