The Sonic Physics Guide Created by Mercury. The Sonic Physics Guide is a comprehensive resource dedicated to describing the inner workings of the classic Genesis & Sega CD Sonic games, along with Sonic Mania. Here, the intricate details of how the game's physics function are thoroughly explored, providing in-depth explanations about the exact values and rules and precise speed values governing Sonic's movements, 360 slope physics, Badnik & object behaviour, all the way to the construction of the sloped terrain. It presents these physics rules in an engine-agnostic manner, focusing on the tangible results of the game logic instead of delving into the minutiae of how the original 68k assembly code operated. Displaying information purely to allow others to understand precisely what's happening and apply those principles to their own fan games. All while still making note of the quirks, limitations, and workarounds the original game had to make due to it's programming language. -- I think many consider the classic Sonic "formula" perfect, and these games have spawned (and continue to spawn) so many fantastic fan projects, and I love to share this technical information in the most easily digestible way possible for the rest of those making their own Sonic frameworks and fan games. To that end, I've been rather dedicated over the last few years in updating and improving the guide, adding any information I find, diving into greater detail with specifics, adding images, or animated visual aid, and being sure information is presented as both general concepts for general application, and game accurate method breakdowns. -- Some of the latest additions to the guide are Refactoring pages Solid Tiles page has been greatly changed, putting a great deal of detail into how sensors work. Information on how Sonic collides has been split into the individual sensors needed Solid tiles has been split into 2 pages, as there was a great deal of slope physics information on a page about tile collision. Slope physics now has it's own page Solid Terrain page, showing how Solid Tiles are used to build complex terrain, along with collision layers + layer switcher objects. Slope physics Extensive details about exact angle ranges used for slope physics with code examples Plenty of imagery Character specific sizes Character hitboxes Slope tile collision demonstrations Game Loop information Explaining the order of events for characters and in what order objects run their code Detailed solid tile sensor information Game accurate explanations of how a detected floor or wall translates into movement of the character Game Object Solidity Added brand new info about how objects behave solid Sloped objects Jump Through objects Specific gimmicks (Seesaws, Flippers, etc) Game Object hitboxes and movements Badniks Projectiles, Particles Character Specific information Character sizes Character moves (with new collision info) Game data Pixels and subpixels 256 angle vs 360 angle systems And more! I'm working on other elements that can go hand in hand with the guide, such as: Lua script overlays for Gens (for all 3 games!) which show an approximation of player and object collision sizes and sensors, to help merge the concepts explained on the guide with actual gameplay to be easier to understand. The first two are out! https://info.sonicretro.org/SPG:Overlay_Scripts I've also been exploring the lighter side of this research, creating a Twitter account to showcase off interesting or funny bugs, quirks, other nuggets of information, and visual examples of collision at: twitter.com/SonicPhysics I don't see much talk about the guide, here or elsewhere. But I know many people make use of it and I hope that more and more people are able to make great use of the guide for their projects as it improves! I hope this thread can allow more people to become aware of it, provide a place for feedback or requests, and to showcase new information and updates.