Lag is a problem encountered by many people that supergem. It causes the game to slow down and makes creating/combining gems hard.
Lag is caused when the demand for CPU power is too high. The computer cannot process so much information and some information will have to wait (like a traffic jam). Commands like create gem, combine gem, gem bomb and other commands can be ignored, thus making the activities hard.
Navigating to another tab helps, as some of the power is spent on animating the shots. Reducing quality also helps reduce lag.