I got this while it was free and it's definitely a fun game. I think if the price is anywhere from 99 cents to $2.99, it would be worth it, and certainly for free. There's a bit of a Boom Blox aspect to it, but this is it's own game. There's no limit on shots, instead the challenge comes from trying to knock the bad blocks off the pedastal without knocking off the homework blocks, which is required to get 3 stars (you lose one star per homework block knocked off). It's easy to win a level, but not so easy (as you get further in the game) to get 3 stars. I haven't gotten that far in the game yet, but so far the challenge isn't that high, so consider this fun, light fare. I suspect it will get a lot trickier as I get further, but if it doesn't that's fine too. This is just a fun little game.
There's a high score of sorts for each level, recording how many shots it took you to get 3 stars, though I'm not sure how compelling that is. I haven't found myself going back to try to finish levels in fewer shots, at least not yet. There's a fair number of levels in the game now and the developer is promising more. Overall this is a great little game and an easy recommendation.
Level 7: Shoot the front roller off the platform before the large book-stack rolls onto it. Without that roller, the book-stack will come to a halt partway down.
Level 8: Shoot the red monster once, turn your view 180°, and shoot the other red monster once. The apples should be closer to the middle and possibly under some monsters. Now shoot the exploding monster. All the homework should stay on the platform.
Level 9: Wait for the apple to roll about halfway down the ruler, then shoot it a little off center. This should cause the apple to roll off the side of the ruler.
Level 12: Turn your view 45° so you have a shot at the exploding monster and shoot it. All the apples should land on the platform.
Level 18: First, get rid of all the monsters except the black one. The black monster and apple should be in their original positions and the book-stacks will probably be resting on the incline. Now, shoot the apple so it falls onto the incline, shoot the black monster off the platform, and keep shooting the apple to knock it back up the incline. A little bit after the last monster falls, you'll win, and the fact that you couldn't keep the apple from falling forever won't matter.
Level 19: Shoot the black monster from your current view. Aim for the very top so it doesn't disturb the ruler when it goes. If it hits the other book-stack on the way down, aim just a little lower next time. Rotate a bit to the right for a better shot and shoot the green monster. Rotate 180° and shoot the orange monsters a bunch of times. If they fall over slowly they might take the book-stack with them, so you want to knock them out forcefully.