Pretty fun, although the hardest part I had was in sector 3, as I kept getting booted off planets, and thus everywhere was either at or near 100%, I just had to wait for passive income to give me enough for new leviathans before I could actually try to take and hold something
Some things that might be worth adding:
Cost Scaling decrease on units that are 'truly lost' (i.e. not immortal)
Some kind of bulk deploy (shift+click for 5 or 10?)
An auto-deploy for units / auto-colonize to reduce the micromanagement and rapid clicking required to take and reinforce a planet before it's taken
I rather liked the audio design, too, so you did well on that!