Talawa Games's Bronze Award-winning subterranean puzzler Unmechanical is free on the App Store right now, so it won't cost you a shiny penny to get your hands on this atmospheric robo-poker.
The game is all about guiding a lost machine through a series of caverns. Each of these caverns is packed to the rafters with switches, doors, and all manner of other contraptions.
It's up to you to discern a way through the obstacles, using physics to your advantage, pushing switches, and nudging things off ledges with your bulbous robo-head.
Unmechanical is a gorgeous-looking game. Talawa Games manages to generate a brilliant atmosphere here as you undertake the various tasks and overcome the various tribulations that a robot trying to escape an underground lair faces.
At review, we called Unmechanical "a hugely entertaining and engaging adventure", although we did have a few problems with the slightly fiddly controls.
Given it's now free, mind, it's a pretty good investment. You'll definitely get a few solid hours of puzzling fun out of it.