The Number Rings resemble large and green floating numbers that are surrounded by a circle of smaller green circles. They always appear in sets of five, each of them displaying a different number from 1 to 5.
In gameplay, the player can earn in-game bonuses by collecting all five local Number Rings in the order of the number they display, starting with the highest (first collect the Number Ring showing "5", then the one showing "4", then the one showing "3" and so forth). The playable character merely has to walk into the Number Ring to collect it, upon which a small sound effect will play. If the player collects the Number Rings in an incorrect order however, the remaining Number Rings will disappear and the player will miss out on the reward they grant. The only way to get the Number Rings back for a new chance to get their reward is to restart the level featuring them.
Sonic Lost World
The Number Rings first appeared in the Wii U version and PC version of Sonic Lost World. In gameplay, the Number Ring sets appear within a general area inside a Zone with emphasis on running or Parkour. Should the player successfully collect all the Number Rings in a set, they will earn a 1-Up, although they must be collected in numerical order.
In Sonic Forces, the Number Rings appear within instanced areas of each and every regular stage, with each stage having one set of Number Rings each. In gameplay, the Number Ring sets in a stage will not appear until after all the Red Star Rings in that stage have been collected. Should the player successfully collect all the Number Rings in a stage, the Silver Moon Rings will appear in all subsequent playthroughs of said stage. Also, when playing the stage again, the Number Rings take on a faded appearance but can still be collected like before. Once all Number Rings in a stage have been found, an icon resembling the number "5" Number Ring will appear next to that stage's Stage Target on the World Map.