Idea for the Stagger Engine
the game is a 3d platformer metroidvania, there are warp rings that take you to stages, in the stage, there are wisps, you can only use a wisp in the main world when you have freed a wisp in a stage. and the wisp can then give you the ability to get to the special stage rings hidden in the main world. entering a special ring would then give you the emerald and a new ability, the special stages are all about escaping quickly, the only thing that's scored is time. the emerald challenge level is entirely focused on the new ability.
also every time you free a new wisp, it'll let you know that you can now find and use that wisp power by showing a little popup on every wisp you haven't used before
retrying a special stage costs rings that you earn by completing a stage, every retry costs more and more rings until you get kicked out, and you lose the emerald. you get kicked back out to the last saved checkpoint with 0 rings. you either have to search around the open world for rings in the platforming areas, or redo a stage to earn more rings as a backup for failing. but either way, you have to do the platforming challenge again just to get back to the emerald ring.
also enemies in the main world that are close to a special ring will have that ability. with there being enemies that try to stomp onto you and crush you when near a blue emerald (I haven't actually decided on what emerald gives you what ability yet, this is just a random example)
you can make combos with emerald abilities, like using a bounce on an enemy in the air will kick them downwards. every combo is recorded in the Miles Electric, or Miles Mini, but you have to experiment and discover each new combo and ability, when you do that, the combo will be recorded so you can see how to do it again, and you can try it out in the training room. you can also spend rings to discover combos for you, filling out the miles electric's combo tree unlocks a special thing (keeping it a secret lmao)
also with the miles electric, you can spend rings to charge up a collected chaos emerald, leveling it up (you can do this 3 times, but its very expensive) for example, the blue emerald bounce lets you do it 3 times- each bounce getting higher- before you uncurl and you lose access to some other arial actions (like srb2 max control sonic) but upgrading the emerald will increase the amount of bounces you can do, from 3 bounces to 5 to 7, and it'll increase the speed and power for the slam