Let's face it, whenever I see a new sci-fi skirmish game, it seems like the first thing anybody asks is "Can it do X-COM?" If for some reason you're not familiar with X-COM, it was an old computer game of tactical skirmish combat that explored fending off alien infantry, raiding their crashed ships, and researching the remains to reverse-engineer all of their cool tech to use against them. Great game.
Gaea Prime: First Defense is basically that: GP's first encounter with alien slavers raiding the Earth for resources, and the adventures of GP's armed forces as they kill the aliens and loot their bodies for research fodder.
Here's how my first game went...