Probably the most straightforward execution of a "speedrunner game." It's not quite focused on actually going fast like the more popular Sonic games so much as it's focused on creating flexible, high-skill ceiling levels which take much time to master. Sonic CD has a genius grasp of how to give the player both interesting levels to cross through and interesting levels to figure out the kinks of so that when the time comes, they'll be able to blast through the game like nothing else. Extremely dense design with convoluted branching paths that fold and weave into each other are usually decorated with a level gimmick/obstacle that tends to, at first sight, impair movement, but actually can be used to increase your speed with the correct knowledge, timing and placement. All of it relies on both stage knowledge and actual understanding of Sonic's movement, a high bar that the games don't usually reach besides demanding fast reflexes every now and again. Quartz Quadrant and Wacky Workbench are the best examples, with seemingly haphazard placement of the stage gimmick gradually making complete sense and feeling perfect as you gracefully flow through the stage every time you play. The real kicker here is that by focusing on this type of branching and gimmick-driven level design, you tap into plain fun platforming and exploration too; gone is the sensation of merely speeding through levels and not thinking (though some may have preferred that), instead you get a great exploratory platformer that offers Infinitely Fun reward if you climb the ladder.