Dash Ring 1-2-3 is the third Challenge Act of Rooftop Run Act 1 in the console/PC version of Sonic Generations. It is unlocked after clearing every Stage in the Modern era and is playable only as Classic Sonic.
This Act takes place within a highly modified version of Rooftop Run Act 1. The stage's layout has been changed with stone boxes, and there are several additional platforms that must be traversed to complete it.
In this Challenge Act, the objective is to reach the Goal Plate at the end of the course while passing through every Dash Ring that the player comes across. If a Dash Ring is skipped, the next one in the set will not function, forcing the player to backtrack.
The Act is otherwise similar to the normal version of Rooftop Run. The player must travel through the stage while going through Dash Rings, avoiding enemies, and watching out for the many Spike Traps on their way to the Goal Plate.