Meltdown moon was designed in 2 distinct phases. The first of these was completely digital, the second was almost entirely on paper.
Here are some of the images from the second phase. As you can see not all of the designs here were used in the final game. Some of the assets were used for more than one thing.
You can also see here the primary task list where we kept track of the bugs and missing features. When working on a small scale like this I find it’s best to keep things low-fi.