Note:
1. You can only open one treasure chest each time you enter the hidden room

2. Hold the up button anywhere in the hidden room to exit back outside

3. There are six treasure chests in total to open. Opening the same chest will not yield more items (empty chest)

4. You can open all six treasure chests by jumping/flying over previously opened chests (try to remember which ones were previously opened)

5. Don't forget to equip the "Lucky Sword" if you have it, to rake in even more cash!