Maverick beat the previous Rumble Racing tracks easily but struggled with Castle Circuit. He blames his sense of direction.
Shortcut to the Castle Circuit Underground

A good start works miracles in Castle Circuit. If you manage to take the shortcut to the underground area, you’re basically golden. It is a lot harder to get lost in the underground , there are tons of boosters and most corners are more forgiving.
To get there, take a left after the first ramp, then after a right turn take the small ramp to jump into the fenced-off area. When taking the corner to the right before this small ramp, it’s important to go at a controlled speed. Go too quickly and you’ll likely miss the ramp, but even if you don’t you’ll fly over the fenced-off area. Go too slowly and you’ll ram into the front of the fence.
Rest of the Race and Checkmarks
Assuming you made the shortcut to the underground, you can take it pretty easy. The optimal path is to go right when you can and stay on top, but it’s no big deal if you fail. Stuck for a few seconds in a corner? Also not a big deal. If you missed the shortcut in the first lap, restart, but if not just keep going.
Each lap you take the shortcut successfully can be finished in a minute or less, even with some setbacks. You need to finish 5 laps in 5 minutes and 30 seconds to complete the Mirage Arena Mission. That gives you an extra 30 seconds of leeway. That means you shouldn’t immediately quit the race even if you miss the shortcut in later laps, as long as you have more at least 1 minute per lap remaining.
The Rapid Racer Trophy

You may think that the Rapid Racer Trophy is more difficult than the Mirage Arena mission for Castle Circuit. In my experience, this is not the case.
It may look like that because it is hard to stay in first place even if you do make the shortcut, but there is a reason for this. The game makes sure you can’t get ahead of your opponents too much during most of the race, regardless of how well you do. This is to make sure the race stays suspenseful. If this is good design or not is not something we’ll get into here 🙂
This system weakens in the last lap and collapses during the second half of the last lap. If you get the shortcut there, you can win. This makes that unlike with the Mirage Arena Mission, the last lap rather than the first one is vital here.
