The Back Star is an acrobatic maneuver used in midair. Its execution depends on the user; Sonic does a back-flip while Amy pushes her body backwards in a flip (similar to the Milky Turn). Regardless of performance, the Back Star causes the user stop and lurk backwards a few feet, thereby rapidly changing their flight direction. Amy notably gains much less distance than Sonic.
In gameplay, the Back Star is quite useful when the user is heading for obstacles or is about to have an awkward landing. Additionally, the move will not cancel the momentum the user receives from the Boost Mode. However, it leaves the users vulnerable to anything behind them. To use the Back Star in gameplay, the player must press the R Button after being launched into midair by gimmicks, like Springs or Ramps.