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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. This is a very difficult round, so finishing it may cost you a few lives. Asterix's version of this round is much easier.

Head to the right, hitting the floating man on the way. When you get to the platform, wait until it is about in the middle of the screen, then drop down onto it. Jump up to the right and quickly smash the blocks out of the way, then jump onto the far right end of the platform and duck immediately (if you don't you'll be knocked off the platform). Ride to the end and continue to the right (ignore the pot). Avoid the spikes and take either route to the right. With the scrolling as far behind you as possible, activate the platform and quickly butt-bash the blocks. Return to the platform and do the same again. Smash the pot for the key, and you are done.