Infinifactory

For some time I was searching for a puzzle game with great replayability.

All the while, there's a fun sci-fi story going along in the background, with dark humor, complete with decent voice-acting, giving you the impetus to keep going.

Starting out simple and holding your hand nicely through the tutorials, slowly introducing new concepts and components, the game ramps up the difficulty massively over the course of its four episodes, but it's never too much of a leap if you have the patience and persistence to keep at it.

Graphics are simple but still pretty good, there's some neat skyboxes and the like.

Optimization is rewarding, so levels are very replayable even if you've already solved them.

The interface is clean and relatively easy to navigate once you get used to it.