The SMB3 Map Editor is an editor created by Beneficii that edits the maps in Super Mario Bros. 3 for the NES. It edits all nine Worlds' tiles and map pointers; it edits eight Worlds' sprites, airship retreat points, starting spaces, pipes, and locks (World 9 doesn't have these). Simply place the program in any folder with a ROM you would like to work with; nothing else is needed. To start, open a ROM that you would like to start editing or one that you've already worked on. When you've completed a map, you can use Export 24-bit Bitmap to save a picture of your map (if your map is one screen, or you'd like to feature one screen of your map, then you should use an emulator's screenshot feature instead. You could even snap four or more shots for an amazing GIF image). The SMB3 Map Editor has eight modes: Viewer Mode, Tiles Mode, Pointers Mode, Sprites Mode, Starting Space Mode, Airship Retreat Points Mode, Pipes Mode, and Locks Mode. When you have worked in one of these modes (except for Viewer; it's a visual) on any map, click Implement Changes or save the ROM. This must be done every time you're about to change Worlds or switch modes. Go to Viewer Mode to see all the changes that you have made so far. If you attempt to open another ROM and cancel it and continue editing a map, then you must use the Save As feature before you can save normally. You can change the palettes (colors) of your maps in SMB3 Workshop. When using the SMB3 Map Editor, left-clicking is for selecting, and right-clicking is for moving. The Enter key will be used often.
The most enjoyed part of map editing is right here (according to most people). That doesn't mean that others aren't as fun, though. Fill the map with a good "background" tile (again, it's not good to have a near-exact duplicate of the original game) and start building. If you'd like, you could place Black Squares (#2) along the left and right sides of your map. You must be aware that there are many tiles that are seen only in non-animated maps (World 5 and the end of World 8, and a few not seen at all)that only have one frame of map animation and three frames used in Tank levels. These tiles include the stars, grassy/hills view from clouds, cloud pieces, Towers, and objects that build and are around Bowser's Castle.
You may remember from using SMB3 Workshop that pointers were things used for objects that can take the player through pipes to another part of the level. Well, there are also pointers used in maps; they are placed on tiles that the player enter. The pointer contains the level that will be entered if the player chooses to enter a tile or one of the Hammer Brother sprites come into contact with the player. Left click a pointer to select it, and right-click a tile to place the pointer there. You can't add or remove pointers from a map. To change a pointer, press Enter. Here, you may choose which level the pointer gets to become. You can even enter custom offsets if you've managed to use extra space. The pointer doesn't even have to be from the same World that you're editing.
You can edit the sprites that are on the map and what item that they'll give the player when destroyed. There are To add a sprite, press the Insert button on your keyboard. By default, this will be added as Nothing--Sprite #2 for Airship. Place this sprite at the bottom of your castle if you don't have the sprite already. This is where the Airship will spawn when a player dies after being inside the castle. To change a sprite or the item received, press Enter. Sprites like the boat, Help, Nothing--Sprite #2 for Airship, (etc...) should have their item set to Nothing. If Nothing is set for a sprite like a Sledge Brother, then once the level is finished, you'll receive an inverted image of a treasure chest. Also, make sure that you try not to place an Airship sprite in some areas of traffic. If you want to use the Boat sprite, then make sure that the player can enter a stage that has no possibility of a death. If death can occur right after the player finishes using the boat, then the Mario/Luigi will be thrown back to the last place cleared without access to the boat because it was already used.
You can choose the location where you'd like Mario/Luigi to appear on the map. If you have not applied the "smb3strt" IPS patch, then the Start location will be fixed at an X position of 2. Applying the IPS patch to your SMB3 ROM will allow you to set the starting position at a free location.
Although you can place the right pointers on your pipes, the new location still won't work. Use Pipes Mode for this. It edits the location of the Pipe Sprite (called "Changes exit location on map" in SMB3 Workshop) in a level that has it. Navigate through the sets of pipes by pressing Page Down to increase or by pressing Page Up to decrease. The sets you go through are in order from World 1 to World 8. Move them to the proper places (the left entrance should be placed at the left pipe in the set; same for right entrance), and press Enter. Click Yes or No if you're doing the Sky Tower or not. Select one of the levels that you're planning to use for the pipe set, and the set will be changed.
Each World has four locks. Set the lock where you want it to be, and be sure to have the right tile the lock will affect under it. Left-click on it and press Enter. Choose what the lock will turn the tile into, then click the BoomBoom button to navigate to the level in mind with Boom-Boom in it. A message will appear; simply click Yes, and a short message will tell you that the lock was changed. If you want an unused lock to be used (or vice versa), then click Make Lock Unused. If a lock is dissolved or a bridge is formed (gameplay) when it's not on the current screen, you will see it form on the current screen; this is simply something visual. When you scroll away or the map is refreshed after coming out of a stage, it will go away. To avoid this, leave the lock event on the same screen.
If you are stuck or need any help, feel free to drop by Board 2, or send an e-mail to email@example.com.