To be honest,I didn't understand how to conquer planets, but I really enjoyed the game as space battle sandbox ;)
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The player is mainly meant to act as a supporting role by attacking other ships and escorting armies. While the army code was bugged in the game jam version, they were meant to invade other planets and take them over. I am continuing work on this game though and have patched that bug and plan to add the ability to call army ships directly to follow you and attack planets you go to. Thanks for playing and I hope you had fun despite that issue!