Device Requirements: Android 2.2 and up
Developmental Appropriateness: So the question here is does it require different cognitive skills/math knowledge to come up with the problem instead of the answer? I think so. It requires more flexibility in thinking - at least at first until you have it all memorized. And from a more practical view, kids don't practice this way of solving math problems as much in school. So in the least, getting the answer is something that may feel more automatic to them while getting the problem may require a pause at first.
Although it might not have been the developer's intent, this way of thinking does kinda prep you for principles like commutativity (3+4=4+3) and inverse (3+4=7; 7-4=?). So this is some untapped potential that I haven't really seen in other math apps. However, here I go again with the need for support and feedback. Nothing is really offered in terms of that. When you get the answer wrong, it just doesn't move on until you do or until the time runs out. So no strategy help is given, hints, prompts, nadda. Also, if kids rely on a certain combination - like if they always choose 3+4 = 7 instead 5+2 or 6+1, then the app should prompt them to try a different way. Further, support that highlights and reinforces the principle that these problems lend themselves to would be amazing. Rating: 3.5/5 (aim for around 7 years).
Balance: There's a game between the levels, but I don't think it detracts from the learning. It actually seems like a good motivator, and the theme of the game (catching butterflies) is related to the butterflies in the task, so it's not taking you to a whole different experience or anything. My only question is whether the colors of the numbers draw attention to certain numbers more. The orange really pops, but sometimes, when the a number is blue and on a blue butterfly, it's not as noticeable. This may affect what numbers kids choose to solve the problems. Rating:4/5
Sustainability: I think this is a nice combination of game and skill. Kids will really like the catch the butterfly "reward" game that adds onto your score. For the content part, you can set it to do different operations (add, subtract, multi, divide). And with the game, there are levels that get increasingly harder. It saves a high scores list, separated for each operation type. One note though that it'd be nice if kids could choose something other than butterflies - in case butterflies really don't interest them. Rating: 4.5/5
Parental Involvement: So not much here for parents - there's no "review"at all - other than maybe the high scores list, but that may be confounded by kids being really good at catching the butterflies instead of solving the problems. If there were prompts as suggested above, that would give parents prompts to reinforce the material as well. Rating: 3/5
Total: 15 out of 20 - 4 stars