Arthropod (World 4-10 or Advanced 30) is the 30th and last level in the Advanced Mode and the 40th level in the game. Arthropod is generally seen as an incredibly difficult level due to strange physics of the feet and intensity of getting into the goal.
The blue goal is attached to the ring farthest away from the start platform and is constantly spinning around with the ring. To get to it, run off the edge of the starting platform and control your speed carefully so that you can bounce along the rings. When you reach the last ring, you have to control your speed and stay on top of the ring without getting squashed by the feet. Wait for the goal to come past, then go in.
However, you can also wait until the clock reaches 40 seconds and rush in quickly. Watch out for the legs! You can also drop quickly to the goal, but this is usually only done by expert players.