Tiles, walls and roofs

Tiles
A tile is a 48x48px area of land that can be placed in a grid through the Creation submenu. Tiles are usually made up of a 2x2 grid of 24x24px subtiles. They are defined with a tileset and automatically connect when placed next to each other.

Tiles have only one toggle - "Not walkable", which decides whether the player can stand on top of it - if it's turned on, the player can't stand on it, and vice versa.

Walls
A wall is a special kind of tile that can have any size as long as it's divisible by 24px (1 subtile, or 0,5 tiles as defined in-game). They adhere to the same grid as tiles - however, they are placed per subtile and not per tile, allowing for higher precision than with tiles.

Other than defining its size in tiles, there are four toggles that a wall can have: "Obstacle" defines whether or not the player can pass through the wall - if it's turned on, the wall is solid, and vice versa. The other three don't do anything.

Roofs
A roof is a 24x24 tileable area that is automatically placed atop a wall. Walls and roofs can be mixed and matched, since they are selected separately. Roofs of the same type will connect, even if they are on top of different walls.

Roofs use the same tilesheet format as tiles - however, in order to keep pixel sizes consistent, in most assets their dimensions are halved - they are assembled from 12x12 pieces.

While making a roof, you might notice two options: a toggle for thick and thin roofs. Much like their wall counterparts, these do absolutely nothing.

Additional notes
As previously stated, most vanilla assets use the same resolutions for tilesheets (96x144px for tiles and 48x72px for roofs) in order to keep pixel sizes consistent between all assets. In reality, as long as a tilesheet's size can be divided by 4px and 6px vertically, OMM will accept it as a valid tilesheet and rescale it as needed - this even works if the subtiles of it aren't square, in which case OMM will stretch them so that they are. While this works with tiles and roofs, which use the tilesheet format, this isn't the case with walls - those will always assume that a tile is 48x48px and a subtile is 24x24px, and will render as such, anchoring the graphic to the bottom left and creating an empty transparent space if needed. This is most likely the second reason for the vanilla tile size.

When walls render, they'll repeat the top 24px of their graphic vertically. This causes the glitch where a small part of them is visible when a roof loops vertically. If a wall is made with an invisible top ~2px, this glitch doesn't occur, and roofs loop properly.

Additionally, walls render ever so slightly offset downwards and stretched to the left. This causes a thin line to be visible on the left side of walls.

Animated tiles are simply animated GIFs. Walls and roofs cannot be animated. Optimized GIFS are currently unsupported and will cause graphical issues - unoptimizing them is reccomended. While OMM does recognize APNGs in the tile picker, tiles with APNG tilesheets will not be animated when placed.