Collected some thoughts and ideas in a big wall of text.
About the cast of characters: What about Vector, E-102 Gamma and E-123 Omega from the original kart game? Maybe they'd fit well into the current game. There are a couple of reptiles already, but no croc. Also those room-filling bots did stand out.
About the single player experience:
- Have more character rotation on the different cups. I haven't figured out the logic yet, but there seems to be an almost fixed cast of chracters depending on the players's chracter. So when I pick Flicky, there is always Big, Blaze and Honey there. Tikal and Chaos Zero after having them unlocked. But mostly it stays the same as the cup before when keeping my main character. I like that the game shows me characters, that I have yet to unlock, especially as someone from outside the Sonic Universe seeing all this colourful cast for the first time.
- Strange cup ideas: A cup where all enemies are heavy (7-9). A cup where all enemies are light (1-3). A cup, where the item that the cup has been named after, appears twice or three-times as often as usual. A crowded cup with 12 racers on probably wider tracks. A custom-made cup (pick 5 races yourself).
- AI: The absolutely brilliant starting procedure could be spiced up even more (when playing with AIs). What if one of the heavier karts becomes a kind of bully at the starting line, trying to deliberately ram other karts? Maybe couple that together with the "Rival" stat on the higher difficulties.
- For the points table in a Grand Prix: Isn't it a bit sad that those who finish last lose all their points from previous races? I think they should be kept on the final results table, maybe because that's how it happens in every form of racing.
About the achievements:
Can the game help me to identify, on which maps I have yet to find a spray can? What about a paint shop in the "Extra" section? Imagine a shop owner, showing me all the colours I have already found, and also having some tasks like "go bring me the spray can from that area...". Maybe with colour live preview? It exists in the character selection screen, but maybe the paint shop would have a mirror, showing the player's favourite kart from two sides.
About multiplayer:
I think the results table gets updated too quickly. If someone leaves during a race (or even after having crossed the finish line), wouldn't it be more clear to have the list keep the names of all participants? Maybe list the disconnected players (those who did not cross the line) as "retired"?
To set up a noob-friendly server, there need to be more options. Especially important would be a track selection, as tracks differ really a lot from each other in terms of feel and difficulty. To not spoiler anything, I'd only allow hosting on tracks that one has unlocked. But you must make the noobs happy, if you want to get more players on board! And everyone started small, never forget that. And some may not want to be that competitive either, but those people still can enjoy this game.
So I'm a happy player with Ring Racers. Sure, the game mechanics are a bit complicated, but that's just a matter of time to get used to everything. The acrobatics / trick system felt wrong in some places though. Two examples were the tracks "Dark Fortress" and "Labyrinth", where some aiming and speed control before hitting the springs would have done it perfectly. The acrobatics feel a bit forced and unnecessary.
Though I feel some missed opportunity regarding the Srb2Kart player base. Because Ring Racers could be a pretty good base for a "simpler" kart racer as well. What about a "Classic cup", including 5 old tracks without shortcut zones or even rings. Disable the ring mechanics for a specific race, if that track has no rings on it... maybe worth trying out? The Ring Racers game physics are already interesting enough to produce good racing without the complexity.
A couple of small ideas:
- ESC Quits the game on title screen.
- Integrate the players keys/button choice in the interface. Maybe you can do that with a tiny font.
- Option for double race length. Has to be applied only on round courses.