I really enjoyed playing! it was tough, but not TOO tough (especially when I realized I could use a controller. I'm no good at precision controls with arrow keys). As for whether you should have stuck with abducting cows vs trying to help shepherd the creation of Earth... why not both?
I actually really enjoyed the little 'mini-game' aspects wrapping around a neat little science/astronomy educational nugget and it kept me engaged wondering what the next mini-game would be or which 'fun space/earth fact' would be next.
Feels like the right scope for a gamejam game and I've bookmarked it in case you decide to add more to it one day.