Snake

there was always a way round.

grid snake on a little reflective screen: swipe, tap or arrow keys to turn, levels that widen the board around you, and after every death the one loop through every cell that would have kept you alive

A Hamiltonian cycle is a loop that visits every cell of a grid exactly once and returns to its start. A snake that only follows it can fill the whole board without hitting itself, because its tail always clears the cell its head needs next.

Concepts: hamiltonian-cycle, graphs, planning.

An interactive you play with one thumb, on Wundr.