useTileBody2d moves a character against the map's tiles: across and against walls first, then up or down against floors. The tiles say what they are in the .tilemap: oneWay for ledges you jump up through and drop down from, slope for the hill, ladder, push for the belts, damage for the spikes, and props for anything else, here the ice the game makes slippery itself.
Nothing is simulated: with step: 60 it is the same game on every machine.
← → walk, Z jump, ↑ ↓ climb, ↓ on a ledge to drop through.