As in classic Mahjong, your task is to match tiles that
1. Have the same designs
2. Aren't "covered" by other tiles.
But here's the difference: You can only match tiles that connected by three "lines" or fewer. Pretend you're drawing a line between the tiles you're trying to match, but your only turns can be right angles. If your path has more than three lines, it's not a valid match.
Keep an eye on the timer! You have 7 minutes for 5 rounds, which is 1 min and 24 seconds for 1 round on average.