The Fever gauge controls Fever Mode, a special feature that forces customers to spend much faster for a short amount of time. The stars needed to fill the gauge increase by 2 with each level and cap at level 16 (32 stars). The gauge can be filled in three ways:
- Giving a customer directions to a random structure (2 stars), which randomly happens on each floor after some time.
- Picking up one of the floating stars spawning on the screen before it reaches the top (1 star).
- Completing Tours with other players or Isabelle (2, 4, 8 or 12 stars).
Once Fever Mode is triggered, the word "FEVER!" appears and the game enters fast-forward mode. Every shop or attraction on the current floor (this includes the Balloon Shop) will randomly generate their expected fees, up to a maximum of 25 Coins for each of them, even if no one is around.
Once Fever Mode ends, everything goes back to normal and shoppers will give the mall owner a random item from the list of unlocked items or a Diamond.