BIGZIPZ wrote:I am actually hooked on that Mummy Maze game that someone posted, so much so I had to buy it! - no editor though, when I get a round to it I might make a 3rd party editor
...I assume you have the author's permission to do this right? It would be a nice courtesy at the very least, I'd think. The author might even save you the trouble of figuring out the file format yourself.
I should note that from an author's perspective, there are good reasons to not release a level editor, despite the fact that all puzzle game developers usually build themselves a level editor in the process of creating the official levels for the game:
1) A level editor for public consumption will need to be tested to be sure it's not too buggy, and have to be at least somewhat user-friendly. This adds to the development time, and might not pay off well, especially if the game proves unpopular and/or too few people care to create new levels.
2) Having a level editor allows the user to explore combinations of game elements that the level designer has never thought about and/or used for the official levels. As a result, there's great potential for the user to expose glitches in the game engine. This may or may not be desirable. (Though generally speaking, as long as it's not a catastrophic glitch, this should not be a problem.)
3) Having a level editor can potentially detract from doing further development work on the next game in the series. I'm not merely talking about Patrick addicted to our custom levels.

By having custom levels, the game author effectively created himself competition, and the bar is raised for the levels in the next game in the series. Once you release a level editor, people will expect all future games in the series to have a level editor as well, so whenever you add a new game element to the game engine, you'd also now need to worry about making corresponding changes to the level editor as well. There're also issues with compatibility--while no one expects levels in the new game to be playable in the old game, they might want custom levels already developed for the old game to be playable in the new game. But such a requirement can be problematic for the new game, especially if the game author wants to introduce new features that necessitates changing the file format for custom levels.
In addition, it might be the case that the author's already planning to develop a level editor, either for the next update of the current game, or for the next game in the series. In which case having a third-party level editor will likely be a disservice to the game author.
So please consider at least checking with the game author before doing anything. I'm not trying to make you look bad or anything, from a game player's perspective a level editor is almost always a good thing, but it's important to realize the implications of doing a 3rd party level editor without the author's knowledge.
(And of course, if you're doing it for personal use only, then obviously it doesn't matter.)