In order to get all of the SP rings, you need to actually know where they're going to be. Oftentimes they're on the top path (which makes sense), but sometimes they're not; it isn't always clear which path you need to travel to next. But even if it is consistently on the top path, you have to know how to get to the path. Sonic Advance 2 gives you zero camera visibility in order to make that decision while you're moving at high speeds, making the upper path very easy to miss. If the SP ring is floating above the ground, you'll miss it unless you've memorized the spot and know when to jump. If it's off the beaten path, above the player and to be reached by spring, or behind a wall somewhere else, you've probably already missed it, because Sonic Advance 2's engine was not designed for exploration and the player cannot be expected to juggle high speed and exploration with the already low camera visibility granted to them.
It's a gameplay model that would have worked on a system with a higher screen resolution and more camera space to work with. The developers should have realized this in the planning stages, but of course this is Dimps we're talking about, so...
