Go check this out – Desktop Tower Defense
I’ll warn you though..it’ll take up so much of your time!!
There is a bit of back story about the developer (and how it’s making him rich!) here which is where i first picked it up from. Almost straight after reading that there was a similar post on Coding Horror where Jeff backs me up in how addictive the game is
I finised the easy level after 3 goes. I managed to finish it straight after that and only lost one life! I’ll be making a start on the harder levels tonight
There are some stategy videos on youtube as pointed out by this post on neatorama but i prefer to figure it out for myself