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For this round the screen scrolls automatically, so speed is a top priority. If the screen scrolling traps you against a wall you die immediately.

Head to the right, jumping holes and avoiding spikes. Smash the pot and grab the red potion. Now wait. When the screen scrolling is just about to touch you, drop down onto the platform. As soon as you can, jump onto the raised surface to the right. Immediately throw potions onto the blocks at the far right. With luck, the blocks will be gone in time to land back on the platform. Head to the right and again bomb the far right of the blocks. Drop down and head up to the pot to get the key.