Ned is a project mainly written in Python, based on the GPL-2.0 license.
NES rom editor
Just type python ned.py
to load the GUI.
To load a new ROM file, use the File / Import ROM menu.
The main window is divided in three parts, from right to left:
To create (and delete) new puzzles, use the buttons below the Puzzle list. The buttons below the Puzzle panel allow you to expand the puzzle with new rows and new columns and to edit the current puzzle. To put graphics in the puzzles, just drag them from the ROM panel to the Puzzle panel. To delete graphics in a puzzle, just drag them back to the ROM panel. Finally the buttons below the ROM panel allow you to display different sets of graphics in the ROM file.
Once you have created nice puzzles and edited the graphics in the ROM, you can save your work using the menu File / Save Dump File. Then you will be able to reload such a file using the menu File / Open Dump File.