As a reminder: skill-based games are not based on luck. When you play gambling games, you place a bet. You follow a hunch or predict. Perhaps even use some knowledge.

gambling, the betting or staking of something of value, with consciousness of risk and hope of gain, on the outcome of a game, a contest, or an uncertain event whose result may be determined by chance or accident or have an unexpected result by reason of the bettor's miscalculation.