After years of playing this, and showing my friends to watch them lose to wave 40+ as well, I finally managed to beat it. There is a surprise wave 51 that scared the crap out of me.
Great time killer, and easy to learn.
I wish there was a stats menu that showed exactly how the towers effect the armor and health.
Hence to show if those 256,000 upgrades are even worth it.
Still one of my favorite TD games to this day.