Invisible Grid

A set of spatial constraints, not visible to the player, determines the actions taken by a character in certain contexts. It is most common in 3D Platformers, but is on the decline. Essentially, it marks where each jump will land and where the next climbable branch is, therefore automating the platform jumping mechanic.

While this takes much of the guesswork out of the process, and therefore allows the player to move quickly without aiming his jumps, it also creates artificial restrictions on the player's actions. One major feature of a game with an Invisible Grid is the lack of an ability to steer in the air.

Common in old Role Playing Games which use Faux First Person 3D.

Games which make continual use of the Invisible Grid, not only for jumping but for walking as well, are often said to be "On Rails", as if the game was played from a railcar. This style of play is common for Light Gun based games and for Adventure Games using a first person view with prerendered scenery. It is uncommon in other genres.

Action Adventure

 * In order to clean up the controls in the 3D The Legend of Zelda games, camera control and jumping were delegated to the computer. For jumping, this worked out to an inversion of Edge Gravity where Link would automatically jump whenever he ran toward something designated as a ledge.
 * Until you put on the Goron's mask in The Legend of Zelda Majoras Mask. The jumping puzzles required then are Nintendo Hard. Missing is common.
 * To clarify, the "jumps" in question aren't actually jumps: Goron Link is capable of rolling into a ball which careens around like Sonic, this is often used in conjunction with ramps to catapult across enormous gaps.
 * The first StarTropics game plays like this even in the action sequences: Mike can only move in the four cardinal directions, and only in single-square increments. When he changes direction, there's a pause before he actually starts moving so the player can turn while staying on the same square. Also, Mike's jumps usually only take him between adjacent squares unless he's leaping over water, pits, or the like, in which case he can jump over that square.
 * If Mike acquires the Winged Anklet, he also gains the ability to jump across 2 'empty' squares. Until he leaves the room, that is.

Platform Game

 * The Sands Trilogy of Prince of Persia had grids everywhere, determining the launch and landing points for wallruns, leaps and chain-swings.
 * The 2D Prince of Persia games were obviously grid-based.
 * Tomb Raider always had them, however, you COULD steer in mid-air to some degree. The much-derided Tomb Raider: Angel of Darkness did away with them, but due to the new system's bad implementation, this was perhaps for the worse. Tomb Raider: Legend marked a return to the series roots but completely removed the blocks and worked on an entirely new non-grid system.
 * Sly Cooper has a sort of "optional grid", in the form of his various climbing and landing techniques. All a jump needs to be is close, then a tap on the circle button brings Sly in for a perfect landing on a wire, vertical pole, or tiny point. Landing on bigger platforms is, in fact, trickier. In addition, all the points he can do this on are marked, representing his "thief instincts".
 * The Oddworld games featured one of these, and made it very obvious by forcing you to use it for puzzles like jumping over mines laid out at certain space intervals (walking moved you one "slot" at a time, a jump moved you three, and a running jump four with another one or two of skidding afterwards.
 * Flashback, like Oddworld, has discretely spaced movement animations. The screen's sixteen "steps" wide, with no in-between, even if you get hit mid-stride.

Puzzle Game

 * Escape From the Mindmaster used an eight by eight grid.

Role-Playing Game

 * Pretty much ANY 2D RPG. Lunar and Chrono Trigger are notable for not having grids.
 * Lunar has a grid, but it's rather fine-grained (characters are 2 squares wide, for instance) and the lack of direct control over the PCs' movements hides it rather well.
 * By default, any game made with the BYOND engine is tile-based. You can hack around this restriction, but the majority of the games made with it will adhere to this trope.
 * Early dungeon crawlers, even 3D ones which were measured in cubes, and all turns were 90 degrees. (See Faux First Person 3D.) Texture repetition revealed the grid. Examples include some Ultimas, Wizardry, and TSR's Pools of Radiance series.
 * The Dragon Quest games on the Super Nintendo are a bit weird about this. The graphics clearly align to a grid, but characters can also take "half-steps" and stand half in one space and another. It made walking around look slightly more natural that way.
 * Golden Sun does this as well, although only characters (and not objects like stone pillars) are able to break off of the grid.

Stealth Based Game

 * The first person stealth game Stolen uses a variation of this. Jumps which could be fatal if missed behave as if handled with a basic physics system, while all jumps in the "normal" parts of missions are scripted. This is semi-justified by the game locked into a third-person camera whenever moving and having to line up animations of acrobatic moves with the environment. You can, however, hop in place almost anywhere.

Turn-Based Strategy

 * Heroes of Might and Magic IV attempted to completely hide the very fine square grid used in combat (a typical unit took up 7 hexes). However, players took it as an Interface Screw, since you could no longer tell if you were moving the furthest you could go, or if you were exactly where you wanted to be. The game was patched so players could once again view the grid.
 * The Nippon Ichi strategy RPGs Phantom Brave and Makai Kingdom have fairly fine grids that usually stay tucked well out of sight, but characters will visibly snap to certain positions from time to time.