I love the gradual introduction of new commands - it's well taught. My design criticism is that the command-line interface, despite meeting the theme, doesn't really add anything interesting in terms of design. For example, in QWOP, removing intuitive control of the player creates hilarity. In Space Command 1980, it's certainly clever and well-implemented, but I'm not getting what it adds in exchange for what it takes away.
Regardless, it was clever and fun and I enjoyed playing it! Thanks for making it!