Great start to some really interesting ideas here! Tower Defense games are awesome, but can often grow a little stale during the 'downtime' of watching your buildings at work. Great choice giving the player a direct slice of action! I thought a lot of your hard-surface work was really cool too!
As for some things to work on, I definitely encourage you to vary up your sound effects a little bit. By creating multiple similar-sounding variations of the same SFX, you can mitigate the issue where the same sound starts to stack on top of itself, which can get pretty straining to the ears!
I think some additional tower mechanics and enemy variety could go a long way here too. What if enemies spawned from multiple locations? What if you could build teleporters to zip around the map? The fact that the player's mind immediately conjures up ideas like those means that you have a great base to keep developing on! Keep it up, good job y'all!