all good suggestions. My maps have colonized planets set to 'rare.

I generally play in a small spiral, and prefer a central starting location. I build many explorers (with extended range fuel cells). The access to discovering ruins first, and abandoned derelict ships / colonizers out weigh the safety of one secure border (edge of map.)

<t> This is elanaahova again. Yes, I agree with both ideas strongly: Les determinism in tech tree, and varied special events in a multi branching story line. <br/>
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Tech would be much better if the R and D only approximated the finishing date. And some special events in various storylines don ...

You mean I am not the sakatauri?

One thing not mentioned, so far, is a low value planet (under 50) is raised by the number of luxuries you have, just as other planets are. So a planet with a rating of 35, with a ruins that ups the rating, and with some luxuries may become a marginal colony.