The rule is small enough to fit in a sentence: the character runs, bounces off walls, and a tap makes it jump. A second tap in the air is the double jump. That is all you get, and it has to carry you 30 kilometres up.
Each floor is one kilometre, ten screens tall. The climb alternates seven kinds of stretch, from breathers to wall-to-wall zigzags, and the difficulty follows a real curve: platforms narrow, steps vary, hazard density doubles between the Gardens and the Crown.
The whole tower is deterministic. The same seed produces the same geometry on an iPhone and on an Android phone, and an automated route proves the summit can be reached without a single checkpoint. Checkpoints exist anyway, for people.
