I just recently discovered that someone named sponge (who was in this forum at one point) made something that lets you load and save maps for Keens 1-3 in a level editor called Tiled. Check it out:
https://github.com/sponge/keen-tiled
I'm not familiar with the level editor, so I don't know if it offers anything new that current level editors like Mindbelt don't have. I thought it'd be cool to share this here, however!
Support for Keen 1-3 maps in Tiled
Support for Keen 1-3 maps in Tiled
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