Lines is a simple but elegant sliding token color-matching game based on the original Color Lines, the first such computer program. It features a "Classic" match-5 mode as well as a "Normal" match-4 mode, AI hints and autosolve, and flawless audiovisuals.
The game starts with three tokens on a 9x9 grid. The player can move one of those tokens to another part of the grid via an unobstructed path, with the goal of making four or five in a row (diagonals included), depending on game mode, in order to keep the board as clear as possible. Every move the player makes without producing a match generates a new three tokens in random spots on the board, which are previewed before the player's move. It's game over when the grid fills up completely with no matches possible.
While there's nothing spectacular about the gameplay, it's hard to find something to complain about in this beautiful implementation.
Sam's Protip: Stumped about strategy? Spam the right-click button and see how the AI handles it.