Enemy and turret artwork is alright, and weapon effects are also good.
For the gameplay perspective, I would say that the early game is too unforgiving for someone who wants to experiment different kind of starts, since it feels like there are too few correct answers to the first 3 waves.
For the second wave, you inmediately need at least 2 upgraded towers, and for the third wave you need a few upgraded + heavy turrets for the bigger enemies.
Right after the third wave, the funds gained are high enough to pretty much build/upgrade a lot of stuff all over the map and test strategies and leave room for experimentation.
I would say that the heavier enemies should appear a bit later, maybe on round 3 (the byped ones) and the heaviest on round 5-6 (the big spider-like things)
Other than that, while having had a few crashes out of nowhere and the lack of sound, it has potential, and encourage you to keep developing it.