To begin with, you are given a sequence of four gems to match. So for example you could get blue, green, green, and red. You must touch one of these coloured gems on the board and then drag you finger to select the remaining colours in the sequence, if you successfully do so, those gems will be cleared from the screen and replaced with a new set, as well as a new sequence to match.
You have a certain quota of gems to remove before the time runs out; doing so then takes you on to the next level, and larger chains to match. Powerups are available to aid you, such as the usual multi-coloured gem which you can use as any colour in your chain… as well as various bomb powerups which remove similar coloured gems in a given direction or radius.