This game is interesting in a puzzle sense, but it is not remotely aesthetically pleasing or even polished. A better version of this game could be programmed in your browser, look better, and not cost any money.
You click cards to total to a predefined sum, gaining points by reaching that sum and not going over. It is not uncommon, however, for the game simply to not give you that card you need to reach the sum. For example, if the sum is 10, and you currently have 9 points, there will be no 1-point cards.
It's a neat concept for a game, but you're better off buying pretty much any other puzzle game. If you're going to spend money on a Steam puzzler, get one with decent graphics that doesn't look like it was made in some high school intro-to-programming class.