From the Super Mario Wiki
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Luigi starts on a platform with the level background very similar to that of The Final Battle. A few platforms and several rotating Spinner pendulums are just ahead along with some ? Blocks. After the first Star Coin and a swinging pendulum, more swinging pendulums and a Red Ring will appear. The second Star Coin and more pendulums are ahead. Afterwards, a Stone Buzzy and a pendulum appear just before the Warp Pipe which will transport the player to rotating pendulums, the third Star Coin and the Goal Pole.
At the last Spinner inside the castle, the player needs to head down to the bottom right corner to find an 8-bit Luigi in a secret area.
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