Gels are gelatinous substances found in Mari0 and Portal 2 that have special effects when applied to a surface. There are currently four types of gels; however, there is no cleansing gel, unlike Portal 2.
Gel can be placed directly onto surfaces in the level editor, or a Gel Dispenser can be added that allows players to place gel themselves. In SE, gel can also be attached to Light Bridges (via dispenser only).
Gel Dispensers produce globs of gel that permanently stick to surfaces. The gel globs can be portaled or carried through Funnels, but they disappear after a few seconds if they do not stick to anything.
Dispensers can face down, left, or right, and can be linked to an input to turn on or off.
The dispenser itself is only solid to Mario; enemies and portal shots will pass through it.
Each of the four colors of gel has a different function. In-editor, gels are referred to by their color (e.g. Blue Gel) rather than the official name, leading many players to do so colloquially.
Repulsion Gel is a blue gel that bounces Mario away. Momentum is conserved, so Mario will bounce back as high as where he jumped from, and as fast as he was traveling. When placed on the floor, Mario can walk on it without being bounced around. On a wall, Mario will always bounce up and away from the wall, regardless of whether he was jumping up or falling down. On the ceiling, it effectively has no function.
The effects of Repulsion Gel are disabled if the player holds down/crouch before touching it. Unlike in Portal 2, the player will not jump any higher from a floor with the gel on it than without the gel. Enemies and other objects are not affected.
The gel can be used to create a bouncy floor, or allow the player to wall jump.
Propulsion Gel is an orange gel that speeds Mario up. When placed on the floor, it will accelerate Mario well past his usual running speed, and even faster still when holding the run button. On a wall or ceiling, the gel has no effect.
Mario will decelerate almost instantly as soon as he is no longer on the gel, including when he runs off a ledge. However, his momentum will carry if he jumps. Like with Repulsion Gel, Mario is not affected by the gel while holding down/crouch. Enemies and other objects are not affected.
The gel can be used to crate high-speed sequences to test the player's reflexes.
Conversion Gel is a white gel that is always portalable. No matter what tile it attaches to, Mario can place a portal on its surface. While it doesn't have much use statically, a dispenser can be used to create interesting puzzles with non-portalable tiles.
Adhesion Gel is a purple gel that was added to Mari0: Special Edition. Any object that touches it will stick to the surface it's on, and can walk along it freely. In the game this is done by changing the object's gravity - for example, Mario can jump away from the wall and land back on it.
The gel is effective on enemies, cubes, and Mario himself. If there is gel on an inside corner, Mario or an enemy will walk up it. However, the gel is not effective on outside corners - they are treated as ledges, and Mario or the enemy will simply walk off the edge.
From Mario's point of view, if he touches the ceiling, or a floor with no gel, he will re-orient back to regular gravity. If he touches a wall, nothing happens. This can be used to create complex gravity puzzles. Note that Brick Blocks and ? Blocks are always affected from the bottom, regardless of Mario's orientation.
Due to a glitch, it is impossible for any non-square object to use Adhesion Gel, including Big/Fire Mario.
- The Repulsion Gel in Portal 2 bounces you higher, while in Mari0 it just bounces you back with the momentum you had. This is probably because of Mario's jump height.
- There is no cleansing gel in Mari0, despite it being in Portal 2.
- The Gel Cannon cheat allows Mario to fire Blue and Orange gel instead of portals. White and Purple gel are not implemented, since Purple gel didn't exist when the cheat was made and White gel would be effectively useless.
- Purple gel is sometimes referred to as VVVVVV gel, named after a game in which the player flips gravity to traverse the game world.
- Purple gel is based on the scrapped Adhesion Gel for Portal 2. The gel was removed for making playtesters incredibly disoriented and even motion sick, but has no such ill effects in a 2D environment.
- Reflection Gel does not appear anywhere in the game, as it would have little use in a 2D axis-aligned environment.