Zelda Improvement

An Overworld Editor for The Legend of Zelda

Background

When I was young and gullible, I was more than willing to attempt all the fake methods my friends described to me for getting the raft to take off from the eastern coast of Hyrule. I loved The Legend of Zelda so much that I was constantly longing for new lands to explore.

Only now, years later, do I actually have them. _demo_, a member of the Mario Improvement team, has joined forces with EFX to produce Zelda Improvement, a utility that lets users edit the overworld data for a Zelda ROM. Now any emulator user can journey through a virtually limitless number of amateur-designed worlds.

At the time of this writing, ZI is only at version 0.1, and hence is still a little buggy. It may always be a little difficult to use, due to the awkward method Zelda uses to store the overworld map. Unlike many hacking utilities, though, ZI can atually be figured out with the help of the only semi-cryptic documentation. And with patience, even novice users can create worlds that rival Nintendo's original.

How it Works

As anyone who's played Zelda knows, the overworld consists of a grid of individual screens, each 8 rows by 16 columns. In the Zelda ROM, each screen is stored as a set of 16 bytes. (Found in offset h15429-h15BB4, to be specific.) The value from 0-255 in each byte represents one of 256 different preset columns.

The hex value 0F, for example, represents a line of bushes at the top and bottom of the screen, with open ground in the center. 0E represents a solid line of bushes. So if you were to replace part of a screen's data with 0F-0F-0F-0F-0E, for example, you would have a small path lined by bushes, leading up to a dead end. There are similar preset columns for lakes, cliffs, cave entrances, even the waterfall. Zelda's entire overworld is constructed from these simplistic building blocks, and you can use these blocks to create your own worlds.

With Zelda Improvement, though, you don't need to worry about hex offsets or what value represents a rock wall. The interface is entirely graphical. Users navigate a map of the overworld, find a screen they want to edit, click on a column, and then flip through all the possible replacements for that column onscreen. With a single keystroke, changes are saved directly to the ROM, ready for playing. It's still a tedious process in this early version, but ZI is a lot easier than using a hex editor.

Designers' Tips

Of course, your level designs need to be compatible with Zelda's multitude of prgramming quirks. Here are a few tips to ensure players can actually beat the game you've designed:

• Entrances must remain intact. If you move a cave entrance to another location on the same screen, users can still get in, but when they exit the cave they will appear where the original entrance was. If you've placed a rock wall there, they'll be stuck.
• Watch out for preset columns with special features. There are two columns with a rock in the center of the screen, and they may look exactly alike, but one of them will allow you to push the rock and reveal an entrance, and the other will not. There are also preset columns with bombable rocks and other features.
• The data for a few screens is duplicated several places in the overworld. If you edit the screen with the faery's spring, for example, those edits will be duplicated in three other places (including the entrance to Level 7, which may become inaccessible).
• Keep users walled in. If you leave an opening along the edge of the map and a player walks through it, the game won't crash, but there will be a weird fadeout and Link will be warped to the center of the screen, possibly getting stuck in the process. The same goes for placing caves on screens where there weren't caves originally.
• Make sure dungeons are accessible! Players not only need to be able to reach dungeons to clear the game, they have to be able to get to them in the right order. If they can't get the ladder from Level 4, for example, they won't be able to clear Level 6. (Of course designing with both Quests 1 and 2 in mind will be difficult.)
• Leave enemies room to breathe. Actually the game is pretty "smart" in this respect; Zolas will only appear where there's water (and only on screens where they're programmed to), Molblins emerging from the edge of the screen will only appear on an open path, and Leevers look for open ground before emerging. If you make a fancy walled-in design with bushes, though, and an Oktorok appears in the center of the screen, it'll be trapped.
• The game tracks whether the player entered a cave by walking down a north-facing entrance or by entering a west-facing set of steps. When the player leaves the cave, they will either reappear suddenly, or emerge slowly, making the walking-up-steps sound. If the preset entrance is in the middle of flat ground and the the user entered a north-facing cave, they will walk up through the ground, which looks wierd.

User-Designed Worlds

Let's see what you can do! If you've done an edit for Zelda, E-mail me, and we'll make arrangements to get it posted here. Be warned, though, that all edits will be rated, and if it's not a quality job I can be brutal. Grin.

What You'll Need

• Zelda Improvement V0.1.
• Legend of Zelda ROM, U.S. V1.0 (No reminder to hold Reset at Save screen.) NOTE: All ROM requests will be ignored.
• An emulator such as Nesticle, for bugtesting.
• SNESTOOL to create an IPS patch (since distributing even an edited ROM would violate copyright law).