It's Sonic Dash (f2p from 2013) with no microtransactions and no ads after runs. Fun little game that doesn't take much time or thought to play. You simply dodge objects and roll into badniks on procedural courses with escalating difficulty. No story. No competitive score leaderboard.

Three Prime characters (Boscage Sonic, Tails Nine & Rusty Rose) are unlocked to start with. Five more (Metal Sonic, Rouge, Espio, Big the Cat & Classic Sonic) are available in the red star ring shop.

Only a limited number of red star rings appear each day. You can randomly get more from end area bounce pads, but it's easier to just play tomorrow instead if you're grinding for something.