Open
button on the toolbar), but remember: it is always a good idea to
make a backup of the original. Once you've opened the ROM you can begin editing
the game. The main window is depicted
below.
Getting Started
The first thing you will need in order to use Editroid is an NES ROM image for the game Metroid. It is your responsibility to legally obtain a ROM image. The maker of Editroid will not distribute ROM files. You will also need to go to the file's properties and make sure the file is not set as read-only (most ROM files are distributed as read-only).
Once you open Editroid, the first to do is open a ROM for editing (click the Open
button on the toolbar), but remember: it is always a good idea to
make a backup of the original. Once you've opened the ROM you can begin editing
the game. The main window is depicted
below.
Each button on the toolbar has a tool tip that identifies its function. If that function has a keyboard shortcut it is shown in the tool tip in parentheses.
Screen Editor
The screen editor is the most important feature in the program. Screens are edited by selecting objects and moving or modifying them. When a background object is selected it will appear in bright colors, as in the image on the left. When an enemy is selected a rectangle will appear around it.
Objects can be moved by dragging them around or by using the arrow keys. They can be modified using the toolbar buttons or the keyboard: use the plus and minus keys to change the type of an object, use the home and end keys to re-order items, and the "p" key to change the color of an object. With enemies the difficulty of the enemy changes with its colors.
The "object info" provides information about what you are currently
editing: The object type icon
(
) indicates the type of the currently selected object or enemy. The types
available depend on the level you are editing. The palette icon (
)
indicates the palette the object is being displayed with. The "slot"
icon (
) indicates which "sprite
slot" an enemy belongs to; when a screen is loaded, if a sprite slot is
already taken, an enemy belonging to that slot will not be loaded. An enemies
sprite slot can be changed by clicking on the sprite slot icon.
The
first item on the status bar is the name of the level you are editing and the
number of the screen you are editing. It is important to understand that you are
limited to a certain number of pre-defined screens which must be re-used to fill
out the map. Use the 
Previous Screen and 
NextScreen
buttons (or the page up and page down keys) to cycle through the
available screens for the level you are currently editing.
Editor Map
The editor map is used to navigate the map while you edit. Click a screen on the map and it will open in the screen editor . You can also navigate the map by holding shift and using the arrow keys. Below the map, on the status bar, the coordinates of the currently selected screen is displayed.
As you edit the game you might want to change the layout of the map. Understand that the map you see in Editroid is for editing purposes only. Changing this map does not generally change levels in the game. The game determines what level each screen represents as you walk from room to room and change levels through elevators. The Editroid map simply aids you in editing and tells the editor which level's data to load for each screen. For this reason, the map is referred to as the "editor map," a map that is used by the editor only.
If you want to change the layout of the map you generally need change the editor map. Right-clicking a screen on the map will deactivate it. During game play the screen will not scroll into a deactivated screen. Holding shift and using the left mouse button, you can paint on the map with the color of the square you initially clicked on. Using shift and right-clicking will cycle an individual map square through all the levels. You can also use the number pad to modify the map.
Metedit
Metedit is a Metroid level editor that may have some features that Editroid does not. If you wish to use the two editors in conjunction there are some considerations you need to keep in mind. Firstly, Editroid saves some extra data in the ROM file. This extra data does not affect any tested emulators, however Metedit is more finicky and requires that a ROM be exactly the correct size. In order to save a ROM file without this extra data, go to the options menu and, under "Maps," select "Save To External File." Also, Editroid's map files and Metedit's map files are not compatible.
It is also suggested that a ROM only be open in one editor at once. If a ROM is opened in two editors simultaneously then every time you save with one editor, any changes made with the other will be overwritten and undone.