About 1.6 hours of a music loop, a couple of different level themes, and a new mechanic every so often that gets gradually introduced. The closest you get top a difficulty curve is between when a new mechanic gets introduced, and the last level to feature it before it gets dropped for the next one; nothing's really given the chance to develop into anything...
Simple fun that will help you pass the time for a couple of hours at a leisurely pace. Endearing artwork helps seal the deal. I'd say it's worth the pennies it usually goes for.
