Your quest is so right,
You can't go left."
In a video game, Ratchet Scrolling occurs when the game screen only scrolls in one direction and prevents the player from backtracking.
This is similar to an Auto-Scrolling Level, except that the scrolling does not occur by itself, but in response to the player's movement through the level. Like the nature of a mechanical ratchet, it scrolls forward freely as the player moves, but 'locks' in place and prevents the player from backtracking.
Lesser versions may allow the player some degree of backtracking, but only to a certain distance or recent checkpoints, while the most extreme versions will keep your character near the left edge of the screen, giving them very little room to move around without ratcheting the screen further.
This is often a Classic Video Game Screw You, especially when the screen is ratcheted vertically, where any platforms that disappear even a few pixels off the screen edge may leave Bottomless Pits in their wake, in defiance of all logic.
In early video games, Ratchet Scrolling was a way to improve performance. If the player could only scroll in one direction, game objects and enemies could be created when they enter the screen and erased as soon as they scroll out, reducing memory usage. A Forgotten Trope now, but was once common, particularly in Platform Games.
- Battletoads for the Game Boy, NES, etc. However, some levels were free-scrolling.
- Almost all Beat-em-Ups and Action Games with platforming elements in the arcade will do this to you.
- All Nintendo-era Contra games featured both varieties of this. Not funny when in a vertical shaft, and you fell off the platforms...
- Super Castlevania IV has vertical ratchet scrolling, making for a few obnoxious challenges if you jump to an area and it ratchets due to overjumping.
- Metal Shark Player's level of Mega Man X6, the second section has you ratcheted, in contrast to the rest of the game (note that if taking the "alternate" second section, it will be auto-scrolling instead.)
- Kick Master doesn't let you go backward; while it's a largely linear game, there are many hidden items that can be missed.
- Layla for the NES, which can lead to some unwinnable situations.
- Amagon featured this as well, one of the last NES games to do so (released in Japan in December of 1988).
- Journet to Silius does this as well and is even older than Amagon.
- The original Glider had this.
- Super Mario Bros.
- The original Super Mario Bros., the Lost Levels Mission-Pack Sequel, and Super Mario Land. The way the levels were compressed required this. The invisible checkpoints in levels were frequently located after a useful power-up, making some players almost pray for Checkpoint Starvation instead.
- New Super Mario Bros. for DS has "Challenge Mode". On side-scrolling levels it enables this; on vertical-scrolling levels it becomes an Ice Climber or Kid Icarus-style Rise to the Challenge.
- The Deluxe GBC port of the original game lets you backtrack to a certain extent, because the game is pixel-for-pixel and the Game Boy screen is smaller than the NES output screen.
- The Super Mario World Game Mod Hammer Brother has this. Unfortunately, you have to go left or backwards at certain points, making it extremely easy to get stuck at random.
- The level called Kinder Surprise in Something uses this particular gimmick. It makes dodging the Kinder Surprise eggs much harder. Also, Mario can take the wrong path at some points, but fortunately the are reset doors available.
- Sonic the Hedgehog:
- The Sega Master System version of Sonic 1 has Bridge Zone Act 2 and Jungle Zone Act 2; the former automatically scrolls right and the latter doesn't scroll down. The latter is thankfully absent in the Game Gear version.
- Sonic and the Black Knight did this, despite being a front-to-back 3D platformer.
- Syobon Action abuses ratchet scrolling to torment the player.
- Ren & Stimpy: Space Cadet Adventures
- A LittleBigPlanet level entitled "When things don't go right, go left" is effectively a basic platformer, apart from the fact you scrolled left.
- The Kaizo Mario inspired level of Pickory will only scroll to the right, but you can backtrack up to half a screen. One trap can only be avoided by exploiting the scrolling and the fact that anything that goes off the left side of the screen is destroyed.
- Adventure Island I and III feature horizontal scrolling limited to the right side. II has arbitrary points after which the screen couldn't scroll backwards anymore, but scrolling is otherwise two-directional. III has two-directional vertical scrolling, with stage 3-6 being the only time the screen can scroll to the left.
- Kid Kool, obviously modeled on the example of Super Mario Bros., disallowed going backwards. Its Spiritual Successor Psycho Fox followed suit.
- Kid Icarus is notorious for its vertical ratchet scrolling - if you fall (and don't have a feather) you die instantly and have to repeat the level. Even if there was a platform just off the screen. Your little wings are no good for flying. This was removed in the sequel, Of Myths and Monsters.
- The escape from Wily's castle in Rockman 4 Minus Infinity uses this, though granted there's no reason for backtracking anyway.
- The platforming stages of Alex Kidd: High-Tech World. (Other stages require backtracking.)
- All of the platformer games in Action 52 use this. One of its top-view games, Dam Busters, also has this, and it can easily get you stuck in an area that keeps you from moving forward, forcing you to reset the game.
- Creatures for the Commodore 64 scrolls only to the right, making it important to backtrack to some bonuses before they get scrolled off the screen.
- Walking your dog in Nintendogs does this.
- Done in the Video Mode for Gottlieb's Super Mario Bros., which features a simplified Super Mario Bros. video game.
- The Video Mode for Harley Davidson: Third Edition has an isometric scrolling road that only goes forward.
- Done in the Video Mode of Doctor Who, done similarly to the Mario example above.
- Sort-of used in Knightmare: the player could never exit a room via the door they came in by. Most of the time this door wouldn't be visible as it was off the bottom of the "screen" but occasionally the entry door was visible.
- In OneWayHeroics, once something is scrolled off to the left, it's consumed by the Darkness and you can't go back. In fact, trying to go off the left side of the automatically-scrolling screen is an instant Game Over.
- Discussed in the comic We Go Forward.