The map editor is a tool found on the main menu of Mindustry. It is a tool where the user is able to use an array of tools to create their own maps that can be played within the game, and also shared with other users mainly through uploading the map's .PNG on discord.
Left Panel Edit
This button opens a user interface, where the user can select the size of their canvas. The sizes available can be set for both width and height, allowing very wide maps to be created. If either a width or height of 512, the largest possible, is selected, a warning message will appear informing the player that large maps may be laggy or unstable.
Load Map Edit
This button, when pressed, will open a UI containing the list of maps that are currently available. This list includes maps that come when the game is first downloaded, and maps that the player has loaded/created. Selecting a map will cause the map to appear in the editor, allowing the user to modify it as much as they want.
Save map Edit
This opens a UI that allows the user to enter a name for their map. Pressing save will then save the map in your editor and make it available in the play menu.