fly with no args toggles flying on/off. Movement commands (fly east,
etc) only work while airborne. "You aren't flying." if you try to
move without toggling on first. Player.flying field tracks the state.
1000x1000 tile world generated deterministically from a seed using
layered Perlin noise. Terrain derived from elevation: mountains,
forests, grasslands, sand, water, with rivers traced downhill from
peaks. ANSI-colored viewport centered on player.
Command system with registry/dispatch, 8-direction movement (n/s/e/w
+ diagonals), look/l, quit/q. Players see arrival/departure messages.
Set connect_maxwait=0.5 on telnetlib3 to avoid the 4s CHARSET
negotiation timeout — MUD clients reject CHARSET immediately via MTTS.