Hexcells is the illegitimate love child of Minesweeper and Picross. Using a series of number clues, you must logically remove and mark hexagons in order to fill out the pattern hidden underneath. If you've played either of the two before mentioned games this will be entirely intuitive, with numbers within a hexagon corresponding to the number of blue tiles (ie. mines) surrounding said hexagon, and the numbers on top of a column signally the number of blue tiles within it (with a few special signals providing additional info).
What Hexcells adds over vanilla Minesweeper is the more puzzle oriented design of its levels, each being individually designed to test your skills of deduction with cleverly disguised patterns that are often far more obvious than they first appear. Solving them is abundantly satisfying, and makes it rather hard to go back to the randomly generated boards of its spiritual predecessor.
But this is also the cause of my biggest complaint, that being the times when logic is thrown out the window and you are all but forced to guess in order to move forward. This is frustrating because you're allowed but one mistake before forfeiting your perfect rating, essentially requiring you to memorize patterns and replay levels or cheat and use screenshots of the completed puzzle to go back and perfect the stage. It's odd that a game essentially designed to entirely do away with the use of luck to solve puzzles falls into such a disappointing pitfall, but I can only assume it was an oversight by the developer as for the majority of the game it's entirely possible to intelligently complete stages, which I suppose is why these moments of guesswork stand out so strongly.
Although it just barley misses the mark, the overwhelming opinion I took away from Hexcells is that of a strong new logic puzzle that has the potential to perfect itself in future iterations, and may one day sit beside the likes of Picross and Sudoku. If you have any appreciation for the games I've compared it to, I wouldn't hesitate to check Hexcells out. It's budget priced so you've got very little to lose, and may find yourself similarly enamored by what at first seemed but a cheap knockoff.