Really hate pay to win aspects on games, I can understand buying cosmetics but not best gear; 4/5. Easy on eyes? No, motion sickness in under 2 hours (I've played other games for longer with no motion sickness); 3/5. Difficulty? Nonexistent for me, too easy; 2/5.
Let me just point something out here to the people complaining about the devs being greedy. The devs of this game have also brought you all the btd games as well and they host them on their own site, ninjakiwi.com, in case you didn't know. And for everyone saying the game is too grindy. Try getting all the actual achievements for the game on their home site then come back here and complain its too grindy. Seriously guys, these three badges here on kong are an afternoons worth of gameplay.
Cute game. I don't normally play games like this and came to check it out because of the badge of the day. It actually managed to keep my attention. Good job. :) Could have been a little bit longer though. 4/5