Labyrinth of the Castle is the fourth and final zone of Sonic Labyrinth for the Sega Game Gear. Robotnik's spooky fortress, this level is significantly less forgiving than the previous three, with bottomless pits frequently awaiting after any mis-aimed spin dash. Projectile-lobbing robots perch on inaccessible slabs of terrain, and flaming arrows fly hither and thither across the long corridors. Watch for pounding guillotines and falling stalactites from above, and keep an eye open for will-o'-the-wisps and crawling flame caterpillars that roam aimlessly around the floor. Conveyor belts flow and cascade like waterfalls. The only way to navigate the stage is to traverse a series of labyrinthine doorways that warp to different parts of the board.
Time limits are as follows: Zone 4-1 = 1:30; Zone 4-2 = 2:30; Zone 4-3 = 3:00. The fourth-act boss is the Smiley Bomb.
||The castle corridors are filled with ghosts and guillotines, arrow-firing bird soldiers and treacherous traps. Watch your step on the narrow walkways - there are drops on each side, and it's a long way down.
— Instruction manual