Short version: great in theory, somewhat well-executed but a tad lacking in focus.
The concept of this game is quite nice, and the aesthetics are simple but pleasing. But "simple" seems to be a reoccurring theme here.
If you were to play the game straight without buying any upgrades, sure it'd be somewhat challenging, but only because the gaps between planes/storks/UFOs and the sheer distance to be traveled can be a bit overwhelming. But, once you get a few upgrades (and mind you, they're not at all hard to get), the game becomes painfully easy; so easy, in fact, I might dare say you could win by accident.
Many of the game's shortcomings could easily be repaired if you had spent more time thinking about the game. Important things, such as impact (how drastic of a change upgrades made), value (how difficult items and upgrades are to obtain), and consistent challenge (making difficult parts easiER, but still not easy), among other things. The lack of these things, especially long-standing difficulty, really makes a normally monumental task as leaping to the moon feel really underwhelming, like getting 3rd place at an elementary school talent show.
The game was, however, quite addicting. Had it been more difficult, interesting, consistent, and in general better thought-out, it would've been worthy of a full five stars.