ROM-gated and checkpoint-gated, skipped cleanly without either. The decode
against the window predicate on every tile the window can answer for; the decode
against a survey of real presses, where every refused press has to be a wall, a
directed wall or a sprite in the way, and every step the cartridge made has to be
one the grid would have planned; GO FRONTIER aiming at ground outside the window
and walking there; and every way out of the map reachable in one plan with no
guessed tile in it.
Pallet Town: 221 walkable, 207 reachable, 90 window tiles, 120 surveyed, 58
refused presses. Viridian Forest: 719 walkable, all reachable, 90 window tiles,
120 surveyed, 74 refused presses, a 215-frame frontier walk out of the window and
ways out 27 to 149 steps away.