I used science to buy cards. Towards the end I averaged a few dozen below science and production each and basically alternated between clearing bad cards and buying new cards with science, wait a turn, build new stuff and buy new cards, wait a turn, etc. constantly dumping bad cards. I feel it's partly my fault for expecting it to be a more traditional deck builder and maybe not fully understanding the 'how to play', but from there are my other comment. That said, looking foward to seeing this down the road! Maybe as a full on combination of - say - Dominion and Settlers of Catan.