It's kind of funny; since I played it hardcore the first day it came out, I ran into my own creation on the second playthrough.. which was mean, because it was the meanest, most brutal combat creature you can possibly build in this game. My poor little kitties got destroyed hard.
My first race, a species of warmongering, world-dominating madmen, are busily fighting a war on two fronts, which means I'm constantly defending my three worlds from assaults. All I want to do now is terraform; that's so much fun, but the game won't let me. My second race is deep into the tribal stage, and going pure pacifists, on hard difficulty, which means everything's inherently hostile. I'm doing surprisingly well, considering... plus, the achievements for beating the game on hard are totally worth it.
The entire game is achievement based; there's the achievements for doing things throughout the game, and the entire Space section is one big achievement farming marathon. To progress, you need badges, which are mini-achievements. Raise a planet's T level, find something unique, fight a war, kill enemies, do missions, etc. Completing badges unlocks appropriate tools for your spaceship; so fight a lot, get bigger and better weapons. Terraform, and get more tools. That, and the universe is freaking huge. While having a galaxy spanning empire sounds awesome, I know you're going to be spammed with "Oh god please come save us from Disaster #317 this week!" as soon as you get more than 10 colonies. It's bad enough with three.