I give permission for this addon to be reused, modified, or ported by anyone
  1. Yes
This is rphys, a custom build containing a total overhaul of the game physics. The changes are essentially:
Global Physics
  • Momentum is preserved
  • Linear acceleration
  • Slope physics are drastically altered
  • Higher gravity, higher jump heights
  • More maneuverability while jumping or spinning
  • Reworked airwalk to only happen under certain conditions
  • Abilities may be used off springs (signified by a sparkle trail)
Characters (gifs coming soon)


Ability: Trick Spin
Double jump to charge a drop dash. Release jump in the air for a small boost or keep holding it for a larger burst of speed upon landing. You can also spin up walls by colliding with them.

Tip: After spinning up a wall, there is a short period where you can use the Trick Spin a second time.

*Special note: Get close to an an enemy with the Trick Spin active to deploy the "insta-instashield".


Ability: Fly
Double jump to start flying for a limited time. Keep holding the jump button to ascend. Hold spin instead to increase your rate of descent.

Tip: To maintain speed while flying, avoid rising when possible.

*Special note: Your flight timer only decreases while ascending.


Ability: Glide & Climb
Double jump to glide in the air as long as jump is held. Glide into a wall to climb it.

Tip: Jumping off a wall will point the camera away from it. Press spin instead to jump without changing the camera.

*Special note: When gliding into the floor, hold spin to transfer your momentum into a roll instead of skidding to a halt on the ground.


Ability: Hammer
Press spin to swing Amy's hammer. Keep holding spin while running to perform a hammer jump.
Double jump to spiral midair and reduce fall speed. Press spin as well to increase fall speed instead.

Tip: Strike a spring with any hammer action to increase its power.

*Special note: The twinspin can also be used to activate the hammer jump.


Ability: Tail Bounce
Double jump to bounce off the ground and most hazards as long as jump is held. This can also destroy some floors.

Ability: Pop Gun

Press spin to fire a cork at the nearest target. Stronger enemies take more shots to damage.

*Special note: Bounce off downhill slopes to gain speed.

Metal Sonic

Ability: Rush Thruster
Double jump to zoom forwards at a fixed trajectory. Collide with a wall to rebound.

Ability: Quick Roll & Speed Booster
Press spin on the ground to perform a somersault. Gain dash mode to change this ability into a booster while spin is held.

Ability: Dash Charge
Hold spin while idle to charge dash mode.

*Special note: Dash mode cannot be lost while in the air, but will only get stronger on the ground.
Extra Notes
Source code: https://git.do.srb2.org/katsy/SRB2/-/tree/rphys

Certain maps may have issues due to the higher gravity. Also, don't even look in the general direction of Axis2d. Just don't do it.

The majority of custom characters should work fine.

Lua can check for the global rphys to detect this mod's presence.

CobaltBW: aerial popgun sprites, original turning code

Chrispy & Lach: sparkles from chrispychars

Logan McCloud: sprite replacements

SuperPhanto: peelout sprites

DirkTheHusky: dropdash sprites

Eidolon & Sal: new uncapped implementation
  • Cool!
Reactions: Windcutter
Extension type
File size
2.7 MB
MD5 Hash
First release
Last update
2.71 star(s) 7 ratings

More resources from Katmint

Share this resource

Latest updates

  1. Various fixes

    There were a few major bugs in v2 (and maybe some banana peels) so I've removed them. Here's a...
  2. Fully featured

    (ignore the spin trail, the green screen messed with it) For some reason I decided to turn this...

Latest reviews

It's a good gameplay overhaul

Great abilities and new colors...
One thing that i found strange is that, on version 3 I'm having problems to play with my friend online, he's getting alot of resynch, when I hosted in version 2 this didn't happen.
Upvote 0
This feels great to play! While not perfect, it definitely feels more natural to control than vanilla SRB2. If you liked reveries, you'll like this mod too. I love the new physics including the new acceleration and slope physics. Version 3 in particular feels great compared to the previous versions. Version 2 was fun but a bit too slippery, and Version 1's abilities weren't exactly my favorite. That's why I bumped the rating up from three stars to four.

However, there are still issues I currently have:
- The characters can jump unnaturally far which makes it harder to control. Try adding some sort of air drag (even if it's weaker than the classics).
- I'm worried that rolling may be too powerful. Try adding rolling friction back to nerf it.
- With Sonic's new trick spin, you can easily lose control since there is no limit to how powerful the ability is. Try adding some sort of cap, even if it's very high.
- I'm not sure if Fang's pop gun is fun enough to use, mostly because it slows you down when you use it. Try making it so that using the pop gun doesn't slow you at all.
- I'm not a fan of Metal Sonic's Rush Thruster at all. I'd rather have some sort of vertical thrust to compliment Metal Sonic's boost mode.

Overall, I think this mod deserves more attention and praise for what it sets out to do. Good luck to you in the future!
Upvote 0
The mod doesn't work
Upvote 0
Interesting momentum mod with new abilities.
Although physics itself is slippery, everyone's getting a little uncontrollable with high speed, so it kinda spoils the impression.

Abilities also interesting enough, I like Sonic's abilities the most, that's a really cool idea to mix Thok and Drop Dash at one ability.

Fang is also fun enough, this Bounce Tail's buff is awesome.

Amy's abilities is weird, but it has good potential with her Athletics-ish tricks. That is really weird that she can't do good badnik bounce at all, Ig that's for balance, so that she couldn't OP badnik bounce with her cyclone hammer.

Metal's abilities is interesting one, I like more controllable version of boost mode, but again, it all spoils slippery controls because of physics.
Rush Thruster is also weird, quite a risky ability to make any mistake like fall to pits, spikes and so on. I can't even cancel this ability, although I think it would be very useful and make Metal more fun.

Tails and Knuckles just have good balance buffs, I can't say anything about that.

Overall, definitely interesting mod with some good ideas, but this physics isn't really good enough to play comfortably.
Upvote 1
The abilities are not working please help
Upvote 0
Some of the physics changes are nice, like the slope momentum and linear acceleration changes, but the air and rolling control puts me off of it. When you make spinning and jumping physics just as snappy as the ground physics, it makes it really hard to jump or roll into enemies at high speeds, since you can't make fine adjustments. Also I just don't really like the idea of sonic having a double jump. It just feels wrong for some reason, like its some b-grade 3d platformer from the early 2000s or something.

There's a lot of potential here, though. I feel like a middle-ground between how this and vanilla SRB2's physics work would be perfect.
Upvote 1
Welcome to releases!
Upvote 0