The Sonic Physics Guide Started/created by Mercury. The Sonic Physics Guide's goal (imo) is to present the mechanics of the original game in an engine agnostic way. Displaying information purely to allow others to understand precisely what's happening (even if not exhaustively listing all of the exact ASM calculations) 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. The classic Sonic games are perfect and they 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 Sonic frameworks. To that end, I've been rather dedicated over the last few years in upkeeping the guide, adding any information I find, diving into greater detail with specifics, adding 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 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. It's 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 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!