I thought it was pretty interesting. If felt like the game play became me maximizing bullet usage. At first I thought I would really enjoy enemies spawning after I killed all of them, but I realized a core part of the loop is waiting, because that time my gun takes to recharge is a resource. I'm just not sure the waiting is super fun for me personally. Maybe refreshing your gun if you manage to kill on enemies currently spawned might help. Just something to reinforce active gameplay. Just my dumb thoughts though, cool submission!