Numba is a deceptive game. It doesn't look very interesting to play, and I suspect the game is one of the cheapest on the Minis store simply in a desperate bid to convince people to be a little bit spontaneous.
Once you get going with it, though, you realize pretty quickly that Numba is a very good game indeed. It's a simple puzzler that requires you to line up sequential numbers on a grid, and although its not too taxing, you will be seeing single digit numbers in your sleep after a session of this game.
There are enough gameplay modes to keep you going for a while, and if you really hooked the game, of course, keeps track of your top scores. The enduring popularity of Sudoku and the like is what Numba is channelling.
The main criticism that can be leveled at this game is that, while it can be played on the PlayStation 3 as well as the PSP, it doesn't really belong on the big fella. It's just a little too basic, and on a console that features some incredible puzzlers, it's not one you'll play much of on TV. If your only console is a PS3, this might not be worth your $3.