So you've fired up Editroid, opened a ROM, and now you've got a myriad of doodads and widgets and whatsits. Where do you get started? How do you make wonderful and amazing worlds with this thing? Well, start by clicking the file menu, and clicking on Create Backup.

Why did you do that? There is no such thing as too many backups. If you intend to create a hack, you will almost certainly, at some point, break your ROM, and you may not even realize it when it happens. Looking through your backups can help you determine when you broke things, how, and may help you figure out how to fix it while minimizing your losses. That's why Editroid makes it easy to create time-stamped backups.

You can use the map to scroll around to different parts of the world. Click the MAP icon on the lower-right corner of the editor to display the map (you can elect to always keep the map open in the View menu as well). For scrolling smaller distances, hold down the middle mouse button (or shift+left mouse button) and drag. Scroll to a location near the beginning of the game for the next step.

Metroid uses “object-based” screens. The screens are built out of pre-defined objects, such as doorways, sections of floor, platforms, etc. You can click on objects and enemies in the screen and drag them around. Re-arrange a room for your first beautiful creation. Use the + and - keys or toolbar buttons to change enemies and objects into different things. Once you've made your amazing room, click Save And Play in the File menu to open the ROM in an emulator. You'll be able to make your way to your spiffy new room and play around in it.

Click on a screen and hit the Previous Screen and Next Screen buttons on the toolbar. (You can also use the page-up and page-down keys.) This chooses which predefined screen to use at the selected map cell. You can also click the Screen Browser button to pull up a window that lets you browse through thumbnails of screens to select one.

You can also click on an empty map cell and click (for example) Brinstar on the toolbar to use this location. (It's important to understand that transitions between areas can only happen via elevators.) You can also click on a used map location and click Disable Selected Screen in the Tools menu if you want to clear that spot.

You'll notice that the game uses the same screens in more than one location (some in dozens of different locations). This is due to memory limitations which only allow us to create so many unique screens. Luckily there is something we can do to fix this.

To enable all the features of the editor, click Expand ROM in the file menu. You'll get a scary warning about how you might break your ROM by expanding it. Not to worry. You thought to make a backup, right? Right? Right?

Once the ROM is expanded, you have tons of space to start adding new objects to screens and new unique screens to the game. Free space is show in the top-right corner of the info box below the selected screen. At the left of the toolbar is an Add/Remove button. It can be used to add/remove objects from the selected screen, as well as to create new object definitions and screen definitions.

Click on a screen in the editor and add a new object (click Add Object in the Add/Remove menu). While you can pick from the list of object types (or “structures”) that already exist, you can also create new structures to make your screens poppin' fresh. Click Add/Remove and then select New Structure. At first, all you'll get for your troubles is a little square of lava. But open the Structure Editor in the Editors menu, and you can create something magnificent.

The Structure Editor is divided into three sections. From left to right, they are tiles, combos, and the structure editing area. For now we'll keep things simple. Select combos from the middle and use them to draw a structure on the right. There are oddly-specific rules regarding how structures can be shaped. There can be no empty rows, and there can not be any gaps within a row. You can right-click a combo within a structure and remove it (within the aforementioned limitations). As you edit your structure, you can see the changes mirrored in the main window.

• Screen refers to a pre-defined screen-sized layout used to construct the map.
• Room refers to a single scrolling area, horizontal or vertical, made up of one or more screens. Rooms are connected to other rooms by doorways.
• Structure refers to the predefined objects screens are built from (also known more generally as objects, as in “object-based layout”).
• Combo refers to the 16 x 16 pixel objects that structures are built from (also known as TSAs or metatiles)
• Patterns (or sometimes tiles) are the 8 x 8 pixel graphic tiles combos are made from.
• An area (or sometimes level) is part of the game map with its own associated graphics, music, enemies, and screen data (e.g. Brinstar, Norfair, etc.). Areas are connected by elevators.
• CHR refers to graphics. The section of the ROM that contains graphics is called the CHR ROM.
• The term item refers to data that places certain types of objects (power-ups, elevators, etc.) at certain map locations. Item data is not part of screen data, and although Editroid shows items in the screens within the editor, item data is generally edited with the Item Editor in the Editors menu.
• Password Tracking Data refers to a list of power-ups and red doors found in the game. When the game creates a password, it checks the player's progress against this list. Any power-ups or red doors missing from this list will not be properly tracked. Therefore, when items are changed and moved on the map, it is important to update the password tracking data by clicking Generate Password Tracking Data in the Tools menu.

While some of the information in the info box is self-explanatory, some warrants more explanation. All numbers are displayed in hexadecimal. Free memory works on a per-area basis. Each area has its own separate memory for screen data.

The default palette is set by clicking the icon. When the default palette is set to the most common palette in the room, the room will load faster. However, an object that uses the default palette will use the palette of objects behind it. The best approach for selecting a default palette is to start by selecting the most common palette, and if that doesn't look right, try changing the default palette until everything shows in the expected colors.

The game has six enemy slots that an enemy can be loaded into. If an enemy is loaded into an enemy slot, no other enemies can be loaded into that slot until the enemy is killed or moves far enough off the screen to be unloaded. If your enemies aren't consistently showing up in-game, try selecting an enemy slot that isn't used in neighboring screens.

Alternate music refers to the creepy music used in power-up and elevator rooms. Click on the icon to toggle whether the screen uses alternate music. There is a limit to the number of rooms that can use the alternate music in each area.

Now that you have a basic grasp of Metroid Editing, you can look through the more detailed articles and tutorials found on the Metroid and Editroid pages.