thanks for the detailed explanation!
I did not have any upgrades, my science team run out of research possibilities some time ago, i wonder what i have to do to get back some options. Is there a techtree (research x requires y (like downed medium ufo etc.)) readme somewhere?. I tried to staff a lot of science but i wonder whether i had bad luck or which critical mission i was missing until then (played a bit longer than two months so far, started on my third base). Suddenly bases and corvettes showing up and i cant down them