Debug Mode

Debug Mode, also referenced as Debug Menu, is the program from development of the game or other software. In game developing, Debug Mode is only meant to be used by game developers themselves for debugging - locating erroneous programming, that can be found by game's testing groups and which will be corrected after being found before the game's final release. In almost all video games, debugging menus are made to be impossible to get access for normal gamers, unless using cheat codes to activate them.

In first installments of Sonic the Hedgehog games for Sega Genesis, Debug Mode can be found by accessing cheat code. When the player has got Debug Mode on during normal in-game, the player is able to break the rules of the game with numerous ways possible.

Overview
In earlier Sonic the Hedgehog games, after activating cheat code, the player may notice "Score" (even sometimes "Time") parts on the HUD having different look, as the debug coordinates of the playable character and screen are located there. The player is able to play normally until he/she presses B-button, that activates Debug Mode in-game screen. The playable character has to turn into different object, which neither is or not seen in-game normally. In Debug Mode, the player is able to move where ever he/she wants.

In this point, the player is able to press B-button again to return deactivate Debug Mode. With C-button, the player is able to select object of the zone and add them to it's place. The objects that are not normally seen in the game can reflect to the player possible concepts for the game, that were planned or supposed to being add during the game's development but could possibly get scraped or become unused. Not every unused content of the game aren't featured in Debug Mode and many of them aren't programmed to work at all. If the player adds too much placements to the one place, it is known to cause lagging in the game. Due the program tool not originally been meant to normal players in first place, the game may erase the saved data in cartridges, CDs or any other formats, if the game gets glitched or crashed by using the Debug Mode.

Some games have also other features that are seen in the Debug Mode. In Sonic the Hedgehog 3 & Knuckles, the player is also able to change gravity from normal to backwards by pressing A-button, in which the playable character, enemies and other objects start raising to the up until bottomless pit or the roof comes a cross.

Known Cheat Codes to Activate Debug Mode
The earlier installments in the series are known to have specific cheat code to activate them, while after Sonic & Knuckles, the only way is to get cheat code, that mostly activates Debug Menus in video games is by using identifiable cheat cartridges, that can read codes such as GameShark. However following list contains available ways to activate Debug Mode in certain Sonic games without using any cheat cartridges:

Sonic the Hedgehog (1991)

 * Sega Genesis: In the title screen press ↑C↓C←C→, the ring chime can be heard and hold then A-button down and press start button to begin the game with Debug Mode. The cheat code only works in US and European releases.
 * 2013 Re-Release: The player has to do particular Level Select code on this version of the game. After coming to the Level Select screen, go to the Sound Test part start playing 01, 09, 09, 01, 00, 06, 02, 03 in order. During the in-game, the player has then tap the upper-left corner of the screen to activate Debug Mode.

Sonic the Hedgehog 2 (16-bit)

 * The player has to activate and have then entered the Level Select screen. There, play songs 01, 09, 09, 02, 01, 01, 04 in order at new Sound Test section. Then hold A-button down and select one of zones of the game and press start.

Sonic the Hedgehog CD

 * Sega Mega CD: The player has to insert Sound Test code in the title screen. Then player adjust FM#40, PCM#12, DA#11 to their own places and then press start button. The player will get then extra picture featuring [[Tails] with words See You Next Game"] from character's designer Yasushi Yamaguchi. The game then progresses to the title screen.
 * 1996 PC Release: The player has to insert Sound Test code in the title screen. Then player adjust PCM#12, DA#11 and then press SPACE in the keyboard.

Sonic the Hedgehog 3 & Knuckles

 * Sonic the Hedgehog 3: The player has to enter the tricky Level Select code and head to the Level Select screen. Here the player has hold A-button down, select one of zones in the game and then press start button.
 * Sonic the Hedgehog 3 & Knuckles: The player has to activate Level Select code and head to the Mushroom Hill Zone (Act 1 is the fastest and recommended choice). Here the player has to jump one of pump elevators and then keep pressing ←←←→→→↑↑↑. The ring chime can be heard, then pause the game and press A-button to head back to the title screen and there to the Level Select screen. There, select one of zones of the game, hold A-button down and then press start.
 * Knuckles in Sonic the Hedgehog 2: The player has to activate Level Select code and head to the Level Select screen. Here, play songs 01, 09, 09, 04, 01, 00, 01, 08 in order at Sound Test part and the Ring chime can be then heard. Then press A-button down, select one of zones in the game and press start.

Sonic Spinball (8-bit)
The 8-bit version of Sonic the Hedgehog Spinball features hidden secrets, that are sort of related to be Debug Mode of the game. On the left edge of each stage is known to have a hidden small chamber, that contains three Item Boxes. Each of them contains 1-Up, Continues, and a special variant with 見る on it (Japanese characters for "look"). Braking this Item Box will give a hint for a secret code. The codes are as follows, to be played in order at the Sound Test of the game in options menu. Putting code right makes the screen do small shake and the code has then activated. Following codes and their purposes:
 * By playing 0, 8, 3, 1, 7, 1 in Sound Test gives the player full codes instead of hints when the player hits the Item Box with 見る kanji on it in each stage of the game.
 * By playing 0, 2, 1, 1, 6, 6 in Sound Test will make Sonic's sprites in general 3 times larger. Despite the large sprites, the game plays normally.
 * By playing 0, 9, 0, 1, 6, 8 in Sound Test makes the player move everywhere in the stage. The player has to pause the game and then press 2 button, thus being able to move around with the D-pad.
 * By playing 0, 2, 1, 5, 6, 6 in Sound Test will give option to skip to the next stage. This is able by pausing the game, pressing down on D-pad to skip the stage to the another one.
 * By playing 0, 4, 2, 5, 5, 7 in Sound Test will make BGM in the stage extremely fast sounding.

Trivia

 * Depending on the game, numbers in Sound Test that are set on to activate Debug Mode are noticed to format specific date, which can also happen when the player tries to activate Level Select code as well.
 * Playing songs to activate the Debug Mode in Sonic the Hedgehog 2 can format date November 24, 1992, that was "Sonic Twosday", while also the game's US release date.
 * This is similarly repeated in Knuckles in Sonic the Hedgehog 2, where putting Debug Mode code can format date October 18, 1994, when Sonic & Knuckles was released in US and Japan.
 * Years later in 2013 re-release of original Sonic the Hedgehog, playing songs at Sound Test for activating Debug Mode can also format June 23, 1991, that is release date of original Sega Genesis version of the game in US and Europe.