thank you for playing. The answer would be lack of time actually. 1st problem, it's not the alien actually , it's the gun not making the gunsound and gunflash properly. So the alien is getting hit. though I see now that I should reduce the alien but 1 hit point more. as for the turret upgrade, I added the upgrade system at the very last day, and it took such a good amount of mental energy to get it working that, in hindsight, would be pretty simple to add a check if turret is there, I was too mentally tired too add it in the end. Maybe I'll add it after the voting period is over. Again thank you for playing.