Second game mode selectable at dog select (host-authoritative online):
- js/sim_arena.js: top-down sim, same export surface as sim.js — x/y plane
plus a z hop axis (Space / comma); KOs by knocking dogs into abyss pits
- js/mapgen_arena.js: mirrored symmetric arenas — walls, pits, center
clearing, guaranteed spawn-to-center corridors, crystals/spikes/launch
pads, mirrored saw pairs; fallback pit pair since pits are the only KO
mechanic
- specials re-imagined per dog: zoom dash, ram + hop-slam, zip-leash
slingshot, blink, hover (floats over pits/saws/spikes)
- render: arena tiles with wall shadows + void pits, top-down dog drawing
with z-lift over a ground shadow; new fall event/sfx
- B.HOP input bit so 'up' can mean north in top-down (Space also jumps in
side view); mode toggle UI + mode carried in start/rematch net messages
Tested: arena mapgen determinism/symmetry/connectivity + chaotic matches +
pit/hop scenarios headless; local chaos + full P2P arena match (host mode
flip syncs to client) in two headless browsers with zero page errors.
