Played: Last Voyage (2015). iOS.

This is fairly short - someone fairly dextrous will get through the whole thing in under an hour - but has immense atmospheric power, making it something I plan to come back to in future. I heard someone describe it as like playing through a Pink Floyd album cover, which is apt enough; the developers describe it as an “adventure through space and mind”, and while that’s a little cheesy, there is a weirdly awe-inspiring quality to the otherwise-simple puzzles it consists of.