I often miss certain information in reviews. Therefore I post it here for people like me, who need it quick and easy.

Playtime: ~20 hrs.
Levels: ~37; from small to huge; bleak design
Backtracking between levels: no
Secrets: no
Achievements: no
Unlockables: no
Collectables: no
Replayability: rather not
Sense of wonder: a bit in the second half