Do you like glowing, neon games? Do you enjoy the occasional brain teaser? If so, you might appreciate Kunundrum.
Kunundrum starts off simple enough, with a glowing circle of light which you have to guide to a target. To move the circle, just slide your finger over it in some direction (up, down, left, right). It will move in the direction you've indicated until it bumps up against a wall or another circle. This simple mechanic is at the core of the game: The trick is in figuring out how to move the circle into the target in the least amount of moves.
Later levels complicate things by introducing multiple colored circles and targets, which mean you have to move the circles in a specific sequence to get them all in place. Later still, you get arrows which throw the circles off their previous course, sending them in a new direction. Continue a bit more, and teleporters come into the picture -- the circle goes in through one portal, comes out through another. So this is a game that gets noticeably deeper with time.
It sounds complicated in text, so here's a video that explains it a bit better:
Kunundrum is offered in two versions: a free version that includes all levels but is ad-supported, and a paid version which costs $1 and is devoid of any ads and distractions. I say, it's worth a buck.