In 1988, Konami published a brilliant puzzle/action game called King's Valley II for MSX1 and MSX2 machines. It was pretty unique in that it came with a level editor that allowed players to create and share custom levels. Today, Beasty Bytes released a new tool to edit these levels on Windows computers.
This new tool allows you to explore custom stages, scroll/zoom in and out, and export your levels to level-map files. And, just for fun, you can check out what your levels would look like in some other classic Konami themes. Check out the website to see how that would look like. Future plans reveal even more new options.
The latest version can be found at Beasty Bytes - King's Valley Spy.