It's an excellent platformer, especially for a free title.
Unless is an exceptional free platformer.
+ Great, colorful, varied, discernible pixel graphics
+ Great platforming, control, environment and gameplay variance, progression
+ Very good tech; snappy loading, resets, navigation, platforming
+ Good story characters (just two; they add character and meaning)
+ A lot of optional and bonus content, speedrun mode, challenges, leaderboards
+ A lot of settings to customize control, difficulty, game behavior, accessibility
* ~70/100 min playthrough (all levels/all levels+bonus levels+10 As)
* Non-voiced text story dialogues
* Limited character mechanics; there's only jumping, with height control; all variance comes through the environment, which I consider a good, well-implemented design
If you like platformers or jump-and-run games, play Unless!
What do you mean by private? If they're non-self-hosted, then they're not private by definition.