Depth Perplexion

The tower is blocking him.

"There's even enemies that you can barely see, like this tiny mouse on the fence in the background. (The tiny mouse somehow hits Dorothy) Like are you kidding me? That doesn't even make sense from a perspective view-point. She's like standing in front of the fence."

— The Angry Video Game Nerd on The Wizard of Oz for SNES

Before the days of 3D graphics, games had three layers: the background, the foreground, and the "main layer" in between that the player actually resided on. Logically, the main layer is where the action happens. Sometimes the foreground might block your view, and some guys may attack from the background, but that's it.

When this trope is in effect, you can throw that thinking out the window. Those Goddamned Bats clearly flying in front of bricks that block you will still kill you with Collision Damage if you get near them. See that thunderstorm in the distant background? It'll kill you if you're in front of it when lightning strikes. If you're lucky, you can use this trope yourself and shoot through walls too, but a lot of the time, only the enemies get that luxury.

This is like Depth Deception minus the logic. The enemy or object in question isn't actually especially big or small... it just somehow affects you even though it shouldn't actually be crossing your path. Depth Perplexion allows developers added flexibility when creating enemy code, allowing them to do things that aren't actually possible, but work intuitively from the game's perspective.

Most of the time, it's a form of Fridge Logic as only blatant examples are likely to be noticed as they're happening. It's very common in Three-Quarters View, and likely to appear in games with Isometric and Side Views as well. Optical illusions such as the Penrose staircase make it Older Than the NES.

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Examples:

• Space shooters in general are likely to allow enemies and their bullets to fly in front of walls in your way, and yet they still affect your layer. Sometimes walls are electric or made of Hard Light that enemies can pass through to avert this. Additionally, since the player's ship's hitbox is usually very small, bullets will appear to pass over it without colliding... unless the bullet hits the very center of the ship.
  • Vertical Scrolling Shooters often allow any primary player weapon to damage both surface and air targets as an Acceptable Break from Reality. Xevious had separate controls for shooting forward and bombing down, but most later shmups have abandoned this. As for enemy fire, it generally has no altitude at all: wherever it is on the screen, it can hit you but will pass through flying enemies.
  • Bullet Hell shooters are the worst, as not only will bullets fly in front of obstacles if present, but also in front of your character, unless they collide with a hitbox. The only way this would work is if the hitbox is actually closer to the player than the rest of the character — which makes sense if it's a cockpit in a vertically-scrolling shooter, but significantly less so if it's part of a person or a cockpit in a side-scrolling shooter.
  • In a surprising version of this, in Ikaruga, not only do enemy bullets not do this, but in the second stage, the player's ship can act as part of the background to avoid certain obstacles. This is because if the ship is lined up perfectly with the one-pixel gap between obstacles, the ship itself will appear to fly under them unharmed.
• Freeware game Action Fist has this issue in the game's second zone, a driving level. Jumping and moving up the screen have nearly the exact same result, except the former makes you come back down. Only averted with the boss, whose lightning attack can be jumped over.
• This is apparently an issue with making 3DS versions of older games. Each sprite has their depth coded into the 3D version, but some objects followed this trope making it hard to tell exactly what its depth was supposed to be. For example, imagine a bullet in an overhead perspective that makes its way from a shooter on the ground to the player in the air; on a flat screen, this can be thought of as the bullet increasing in height (moving towards the front of the screen) as it reaches the player. In reality, it was just programmed as a 2D bullet; no problem until you're trying to code in how close it should be appearing on a 3D screen.
• Echochrome is Depth Perplexion: The Game. It's all about playing with depth and perspective: if an obstacle can't be seen - say, a gap in the ground that you've put behind a pillar - then it doesn't exist, and your player character (a little wooden artist's mannequin) will travel across it no problem. There are plenty of Escher-like paths to confuse you as well.
• The exact same mechanics apply to Naval Warfare.
• Stone of Life EX registers a hit when the player's attack sprite hits the enemy sprite, while the game is on an isometric playing field. The player can attack by waving a weapon in front of an enemy sprite.
• In Mystery Quest for the Nintendo Entertainment System, the bats can and will fly through the ground and other solid objects.
• The Digipen Game Perspective is all about this. You can switch from controlling the camera to controlling a character from a 2D platformer, and you can walk from one wall to another in 2D mode.
• In the first level of the Shifting Sand Land state of The Adventure of Little Ralph, there is a bleached skull that is in the background. Later in the level, there are bleached ribs, also seemingly in the background. Since the first bone seen was a background element, the ribs must be, too. NOT! The ribs are actually Spikes of Doom that impale Ralph. This may give players an unwelcome and bloody surprise.
• In Trilby: The Art of Theft, guards tend to pass right under your sprite. The catch is you're hugging the wall farthest from the screen, meaning they should be layered on top.
• In Bloons Tower Defense, things can get confusing when it comes to flying monkeys like the Ace and Helicopter. Their projectiles can pierce through several bloons in a straight line, implying that the bloons are at the same altitude as them. Yet bloons are also affected by abilities that are clearly on the ground, such as piles of tacks. And the flying monkeys are also clearly flying above them, not low to the ground, since they go over impassable terrain.
• In Castlevania: Dawn of Sorrow, the Final Boss (Menace) can hit you (for a lot of damage) with a foot that is clearly in the background behind Soma. It even is of a darker shade to emphasize that is indeed in the background.
• Obvious in Deadly Towers. The game uses an isometric perspective, but hitboxes surround entire sprites. Many sprites are much taller than they are wide, resulting in hits registered (on both enemies and the player character) even when, logically, no contact should have been made.
• In Dwarf Fortress, not only can you attack in all eight directions (and projectiles can be fired toward any square on the screen), the game currently has three dimensions but altitude has no effect on ability to attack: a fish in a river and a dwarf on the surrounding cliff face are perfectly capable of exchanging blows so long as they are horizontally adjacent. In adventure mode, you can even attack units underground if you happen to be directly above the 3x3 tile square that unit in is the center of and have at least one visible target in range.
• In E.T. the Extra-Terrestrial, E.T. would fall into a pit if he touched it with his head.
• Equinox is an early 2D game that simulates a 3D isometric environment. There is a minor Depth Perplexion glitch that can occur in the game due to the graphic layering that performs the simulation. Read here for a good explanation.
• You can't walk behind flowers in pot in a table in Final Fantasy IV.
• An odd variation with the FL-3 "Shark" laser weapon in FEAR 2: Project Origin. Rather than ironsights, it uses a Laser Sight emitted from the muzzle, replaced with its actual cutting laser when you pull the trigger, to aim it. The problem is that someone apparently forgot how to properly program the weapon to always aim for the crosshair at the center of the screen, so the laser always shoots out straight from the muzzle rather than adjusting based on what your crosshair actually passes over - the end result being that, past a couple feet, the laser shoots out towards the upper left of the screen, requiring you to aim down and to the right to hit targets if they're beyond a certain distance.
• Very evident in Gatling Gears. Almost all projectiles exist on one plane, so bullets and enemy rockets will ignore walls, structures and terrain, no matter what elevation. You can take advantage of this, however - for instance, targeting air units in the same way as you target ground ones.
• The Glider games had balloons, copters and darts that could fly in front of furniture (deadly to crash into) but caused Collision Damage all the same. The games never had a strong sense of layering (it mostly affected graphics); it's remarkable that the thunderstorms in Glider 4.0 don't kill you.
• Part of a puzzle in God of War III; the puzzle shifts the camera to the perspective of a statue overlooking the area, so that stairs, walkways, aqueducts etc. look like they're connecting to each other when in the 3D world they're nowhere near each other. However, since this is Olympus and the statue is magic, while the effect is active you are able to treat the "illusion" as if it's real, and thus beat the area in ways that would be impossible with normal dimensions.
• Golden Sun suffers from this, in that sometimes, due to the overhead view, it's difficult to tell if a pillar is standing upright or lying down. It can also be tricky to gauge distance between platforms, resulting in several minutes of random wanderings until you accidentally stumble across the solution. Thankfully, it only happens occasionally.
• Indiana Jones and the Temple of Doom for the NES is a jumble between an isometric 3D view and overhead view, leading to this.
• In Keychain of Creation, a resident Reality Warper uses "broken perspective strike" as one of her attacks. Her blade comes nowhere near her opponents, but the images for both overlap, therefore the enemies get hit. They are as confused as the reader.
• In Kirby games, some copy abilities as well as Kirby's inhale can reach behind walls. Whip can reach items behind walls, and a fully charged Spark (starting with Kirby's Return to Dream Land) or Plasma will always go all the way across the screen. Using this to your advantage is required in a few of the games' puzzles.
• La-Mulana's most common enemy is a bat (in two sub-types) that flies "in front of" the walls. And it's definitely of the Goddamned kind. And because they are of the same color, they seem to fly BEHIND water and other objects that are behind your character.
• The Legend of Zelda
  • The Legend of Zelda CD-i Games had numerous problems with that. For an example, a top part of one of the pillars blocks the player but the bottom part doesn't. Many screens use painted landscapes that have a lot of depth, but the gameplay is strictly 2D as shown here.
  • The Legend of Zelda: Link's Awakening uses Three-Quarters View but lacks Z-levels—the jump ability instead just makes you momentarily immune to falling through holes in the floor. It's possible to, say, hit an enemy on the ground while swinging the sword at the crest of a jump because Link and the enemy are at the same height on the screen, even though perspective implies that the enemy is below and to the side of Link. This was fixed in The Legend of Zelda: Oracle Games, which use the same engine, as well as the Nintendo Switch remake, which uses actual 3D graphics and thus has an actual Z axis.
• Little Red Hood is supposedly in a 3/4 overhead view, but if you jump in front of a tree, your head bumps into the trunk. Another AVGN explanation is at the 11 minute mark here.
• Since enemies in Live A Live take up multiple squares on the battlefield, there are plenty of times when you're blocked by them when it looks like you could just travel behind or below them.
• Metroid II: Return of Samus: Remember how getting the more aggressive green Metroids stuck on bits of scenery was viable tactic in the first game? This time around it's turned against you, as several enemy types can pass through material Samus is hindered by, including the Metroids, who are all immune to your fancy shoot-through-walls weaponry. Although larval Metroids are not among them; it seems they are still required to play by Samus's rules until they grow up a little.
• Pretty much the same problem was present in the overworld of Mickey's Racing Adventure for the Game Boy. The Treehouse Glade in particular is made rather maze-like by your inexplicable inability to walk behind trees.
• Monument Valley's core gameplay is based around the same mechanic.
• In The Mummy Demastered, flying enemies can and often do pass in front of solid walls.
• In the Nintendo Wars franchise, planes can fly over any space, but can't pass through spaces occupied by other units. Even ground units. Even naval units. Even submerged submarines.

• Pokémon
  • In the original Pokémon Red and Blue games, the player character could only move over objects or be blocked by them; thus, you could not, say, walk behind a skyscraper; even a road couldn't pass behind it, because it's blocked by your game perspective. This was changed in Pokémon Ruby and Sapphire where you could walk behind lampposts.
  • This trope was still in effect in Ruby and Sapphire, and it was actually more baffling than before. Whereas in previous games, you knew that you could never walk behind a building as even its roof would block your way, Gen III was far more inconsistent with this. For instance, you could walk behind a building, but its collision data treated it as if it was wider than its graphics depicted it as, so its the highest parts of its walls would block your path even though it was evident that you weren't touching them. For example, by looking at a Pokémon Center's roof one would assume that the building is only one or two tiles long from south to north, whereas the collision data seems to think it's actually three tiles long (meaning that 3/4 of it was solid). And then there was the Cycling Road, a bridge that had areas that allowed the player to walk under it, as well as areas that blocked him or her despite having nothing under them.
  • Gets even more egregious in Pokémon Diamond and Pearl and later, where this is still in play, even though the game is now rendered in 3D. That's right, now you can see what's behind those buildings thanks to perspective, but you still can't actually go there, even if it looks like you could. For example, there are several places where you can clearly see one tile of space between the north face of one building and the south face of another, but the game will not allow you to walk onto that space.
• In the C64 version of Rambo, the tops of palm trees would block your path and had to be blown to smithereens with explosive weapons if you were to pass. All the while non-explosive projectiles from your and your enemies' weapons freely travel through everything.
• The NES game Robin Hood: Prince of Thieves was insane with this, as shown in the picture at the top: Much like the Little Red Hood example above, the game played out in an isometric perspective, which factored into the collision detection, forcing players to swerve around towers so as not to walk straight into their peaks on ground level.

• Rygar had this issue in the overhead areas. If you jump, your Diskarmor would register a hit on whatever was in the same place on the screen, even though your hero's shadow was about six tiles below. Savvy players could use this trick to easily defeat one of the bosses.
• Some of the beams in the New York level of Samurai Zombie Nation come from the buildings in the background, but they damage you just the same as the ones in the foreground.
• The Simpsons: Bart vs. the Space Mutants for the NES is basically a Side View 2D game with graphics made to look like you're in a 3D enviroment.^note Although the skateboard part of the first level allows you to move up and down and not get damaged by enemies in the background, but this is probably through some clever use of smaller collision boxes (the enemies aren't high enough to reach your face or torso) and the skateboard working pretty much like a jetpack. This sometimes allows you to stand on the horizon or cross a river by jumping to the background where it's more narrow (but you're still at the same size).
• Sonic the Hedgehog
  • In Sonic the Hedgehog, Batbrains can fly through walls in the Marble Zone.
  • Against the Final Boss in the second game, the giant robot's claws are to the sides of its torso, but if you try to hit the robot while one of the claws is extended, the claw will kill you.
• In StarCraft, it's possible to shoot between high ground and low ground even if the ground should be in the way. It's also possible to shoot from low ground to low ground when there's a wall in the way.
• Super Mario Bros.:
  • In Super Mario Bros. The Hammer Brothers are late-game enemies, known for being incredibly difficult to pass or defeat. They can jump up and down through blocks. The hammers they throw also ignore terrain.
  • Super Mario Bros. 2 has Pokeys that go right through cacti, even though the cacti block you. And you can stand on top of the Pokeys, as well, "riding" them past the normal cacti.
  • Super Mario Bros. 3: You can hide behind the background of certain levels. This is wholly intentional, however.
• Many, many Super Mario World hacks come under this if they use graphics not meant for 2D platformers (like isometric ones or three quarters view ones from games like Trials of Mana). Good luck figuring out where the floor is solid and where it isn't in levels like Dark Castle or Dragon's cave in Brutal Mario for instance. Or which bosses are foreground and which are background in the same game.
• In the Onett stage found in Super Smash Bros. Melee, Brawl, For Wii U, and Ultimate, players are fighting on a grassy path in the space between two houses, yet they get hit by cars that drive on the road in front of the houses.
• Sunset Riders has a level where the players, while standing on top of a train, could shoot and be shot by enemies attacking from the windows of the train, which would only be possible if everyone had bullets that magically curved like a boomerang.
• In Syobon Action, you might jump in front of a cloud in the background before developing an irrational fear of clouds.
• In Terraria, Fire Imps can throw fireballs in front of blocks, but most of your projectiles get blocked by them.
• Transformers: Convoy no Nazo has solid blocks that the player can't shoot or pass through. Enemies fly in front of the bricks, but they still kill you with Collision Damage if they touch you.
• The Ultimate Stuntman: The gliding segments attempt depth by letting you increase/decrease altitude, which changes the sprite's position on the y-axis and size if it's high enough, though it's hard to tell at what height other objects are and trying to fly through holes in walls (as you can't go over them) is nerve-wracking.
• Warcraft II: Tides of Darkness has submarines which can only hit other ships; they can hit over land. This is a limitation of the pathing code of both games, although it's made up by the fact that a unit that shoots another makes itself visible (and thus shootable) even if you wouldn't see it normally.
• Warrior Cats: In the online Hunting Game, enemies can travel through tree stumps that you can't get past without jumping over them.
• Wayne's World (Gray Matter) has a level with poles that are clearly in the foreground, but still block players walking on the sidewalk.
• The Witness: In the environmental puzzles. A circle can be made of multiple objects that are lined up just right, then the line being traced can hop around various things that are disconnected from any other angle.
• The Wizard of Oz for the SNES features some incredible examples. At one point, Dorothy is attacked by a mouse sitting on a fence in the background. You also need to jump on top of a large hourglass to progress, which looks like a background object, considering that half of it is behind a grandfather clock which you can walk in front of.
• Wizards & Warriors: The first game game has floating tree stumps in the forest level.

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