The hint button is at the top of the game screen. Both helps come after a short video, and only if you choose to watch it.
A hint
A hint turns one card face up for 3 seconds. If you already turned a card, the hint shows its partner. If no video is available, you still get one free hint per game.
A second chance
In Timed, when the time is up, Keep playing gives you 15 more seconds. In Survival, when you are out of lives, it gives you one more life. Once per game.

