I mostly agree with others as the game needs to be balanced and something to do in between waves would do aalot for it
Maybe we could just aim the gun or maybe we could buy ourselves some upgrades aswell, like clicking the ememies to dmg them so the auto aiming sentry can easily kill them.
Or maybe 2 types of enemies, one which the sentry will take care of and a separate type of enemy that you have to click to kill and will be ignored by the sentry
This could also help with the theme implementation. Like the duality is the sentry fighting the enemies which it can hit and the player helping it by targeting the other enemies!
Some more visual and audio feedback to taking damage, firing, changing target enemy would be nice aswell!
The art design and ui elements look fire!
Some small changes and a bit more features and this game will bee a blast to play!