OK, the reviews were right
I played this game out of curiosity after reading the negative reviews on the site. There are no projectiles, fixed tower placement positions, and tower types that really don't seem to do anything special. I played up to level 12 or so, and then the game locked up and took my browser with it. I had to forcibly quit Firefox and restart it.
This game could be made much better by increasing the stability, and then adding some basic features like free tower placement, projectiles, and revised artwork. (For instance, the tower images are so large they completely obscure the oncoming enemies).