The graphic presentation is fairly simple, but this is a deceptively deep Dr. Mario-style puzzler with a unique color-matching mechanic. Whenever you make a match, you leave behind a ball of a new color, and your job is to work your way up to the top of the rainbow scale. This adds a lot more gameplay dimension than you'd expect, and once you get into it, you will be hooked, trying to make that last couple of levels. Definitely give Combine a chance.