Sonic the Hedgehog 2 is a platforming action video game. Developed by Sonic Team and Sega Technical Institute in 1992, it introduces new mechanics to the series, and the lovable young fox known as Miles "Tails" Prower. The massively successful sequel to the original Sonic the Hedgehog, Sonic 2 stands as the second best-selling Sonic game in history, and is considered by many fans as the best Sonic game.

A 2-D side-scrolling platformer, you control Sonic, a blue-colored hedgehog that runs pretty darn fast across the stages (zones as they are called in the game). Alternatively, the player can also play as Tails, who either functions identical to Sonic. Scattered throughout the zones are golden rings that Sonic can collect, which allows him to not only take damage, but allow access to special stages. The special stage, which is now a pseudo-3D tube, involves collecting a certain amount of rings and avoiding bombs.

Returning from his previous defeat, Dr. Ivo Robotnik plans world domination once again by kidnapping and converting animals into robots, and collecting the seven Chaos Emeralds. Unlike his previous frenzy with Sonic, Robotnik has built the Death Egg, a giant battle station orbiting the Earth, and intends to conquer with it. Sonic (now followed by Miles "Tails" Prower) set off to collect the Chaos Emeralds and defeat Robonik once and for all.

Sonic 2 with Knuckles is a ROM hack of Sonic the Hedgehog 2.

This ROM hack aims to be a gameplay enhancement of Sonic the Hedgehog 2, including features and mechanics from Sonic 3 & Knuckles, as well as some original features.

The core additions of this ROM hack are the following:

- Insta Shield: Sonic can perform an Insta-Shield, allowing him to become invulnerable during its execution, extend his attack range and even deflect some bullets. This can not be executed in 2P Versus.
- Rolling jump lock cancellation: Much like in Sonic 3 & Knuckles, using the Insta-Shield allows for cancellation of the rolling jump lock, a mechanic present across the original quadrilogy on the Mega Drive. This can also be triggered any time the Insta-Shield is impossible. This can not be executed in 2P Versus.
- Flight: Tails can fly, as well as pick up Sonic in the main game's two player Co-op mode. Just like in Sonic 3 & Knuckles, Tails can also deflect bullets while flying.
- Knuckles: Knuckles is now a playable character, who can be selected from within the options menu. He retains his gameplay style from Knuckles in Sonic 2, but can also destroy monitors while in a gliding state, as well as deflect bullets.
- Improved pausing mechanic: Pausing is now player dependent. If player 1 pauses, only player 1 can unpause. Same goes for player 2.
- In-game player swap: The two players can swap controllers virtually. This can be achieved during a pause, with both players pressing the A button. This feature is meant for use on emulators with netplay capabilities.
- New transformation method: To turn into a Super form, the button combination is the same as for the "Multi-Button" option for Sonic 3 Complete (Press a different face button from the one you used to jump with.)

In addition, there are numerous bugfixes, most courtesy of the writers of Sonic Retro's Sonic Community Hacking Guide How-Tos.

Additional thanks go to the maintainers of the Sonic 2 Github disassembly, and the contributors to the Sonic 2 Community's Cut disassembly.

Database match: Sonic The Hedgehog 2 (World) (Rev A)
Database: No-Intro: Genesis (v. 20210226-213851)
File/ROM SHA-1: 8BCA5DCEF1AF3E00098666FD892DC1C2A76333F9
File/ROM CRC32: 7B905383

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