While in the game's main menu, scroll down to the "How to Play" section, it contains a detailed explanation of the game rules and some useful tips.
Show hint - unlike other games, there are unlimited hints.
Toggle highlighting of free tiles.
Reset zoom, you can zoom in and out using the mouse wheel.
Open the game's menu.
Reshuffle the board.
Press P to pause the game.
Press H to show a hint.
Press N to start a new game.
Use the mouse wheel to zoom in or out.