I'm a sucker for tower defense games. Every year or so, I get the hunger to play one when I want to feel kind of brain dead. Usually on my phone though. But yeah, I've recently grown kind of addicted to this one. One of the reasons is that every death in the game is a lesson. So when you die, you're like 'OhhhI died because I made this mistake. So next time I must XYZ.' So, by your fifth playthrough you've acquired all these lessons under your belt.
Also the recent addition of the pause button between waves makes the game significantly easier.