Good quality reverse Tower Defence (Tower Assault?). Game mechanics are simple with 6 unit types vs 6 tower types. The story introduces new game elements at a perfect pace. Achievements are mostly easy. The Advanced difficulty ones are clever and put a twist on each of the 14 missions similar to Starcraft 2's Hard Story achievements. Further replayability is there with the contrasting gold medals forcing you to play each mission differently. Tokyo Raid gold medals are very time consuming and challenging though so it's not all easy. Highly recommended.

Really good casual puzzler/platformer. Low difficulty and keeps fresh with new game elements for the duration of the 8 or so hours it lasts.

Turned out to be a surprise win for me. Didn't expect much, but was a really fun set of about 50 or so missions. Difficulty goes way down low, you can set the controls to "arcade" mode and just fly around kicking ass.