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.
fly <direction> moves the player 5 tiles, ignoring terrain. Leaves
a trail of bright white ~ clouds that fade after 2 seconds. Effects
system supports arbitrary timed visual overlays on the viewport.
TinTin aliases: fn/fs/fe/fw/fne/fnw/fse/fsw.