There are two major modes in the game: persistence and existence. The former requires patience, a stubborn resolve, and chamomile tea to prevent your nervous system from frying itself. The levels are long and often tense, and one mistake sends you back to the beginning. Existence is much more casually-oriented and features shorter levels and less-stressful gameplay.
Another nice touch in the game is the ability to view background artwork and play any stage at your whim. It takes some of the pressure of completion away and allows you to experience more of the game.
Overhead Persistence is actually part of a series of "overhead" games with a similar "don't touch the walls" design. Each one has a unique theme, though Persistence is the most polished and complete of the lot.
Analysis: Overhead Persistence is just like any old maze game on the surface, but the beautiful visuals and soundtrack make it special. The creative maze elements (such as moving doors and swinging objects) make it exciting and challenging. The parallax backgrounds are a nice touch and add a lot of depth to an otherwise flat game. It's the same old mechanic at its core, but with so many bonuses it's hard to overlook.
Cheers to Tim for sending this one in!