Every game that is featured on this site is either completely free with no advertising, has a one time up front cost or one time IAP to unlock the full content ad free.
All screenshots are from a Nexus 7 2013, full sized and un-cropped.
AFAIK, Kingdom Rush is not IAP-free. Levels are easily beatable by buying power-ups. Without them, I found that after a level or two, it got very difficult, and I couldn't pass. I got the distinct feeling I was supposed to start buying power-ups (cheats, really) to win. Too bad, as it looked very solid otherwise.
I'd also add that Osmos is a fantastic game. Very soothing and fun. Frozen Synapse is a terrific game (turn-based, simultaneous tactical shooter (drop-down)), and I wish there were more like it.
Maybe Android is different, but about a year ago I beat Kingdom Rush on an iPad without purchasing any IAP over the course of a Sunday afternoon. Yes, later levels were hard, but definitely not unbeatable.
It's possible that they've changed the difficulty since in order to make people pay for cheats
Pixel dungeon is one of those games that you need to sink 1-5 hrs into before it starts to get fun. Once you know the basics though it's super fun to play and very addictive.
www.honestandroidgames.com
Honest Android Games
Every game that is featured on this site is either completely free with no advertising, has a one time up front cost or one time IAP to unlock the full content ad free. All screenshots are from a Nexus 7 2013, full sized and un-cropped.