Computer game of the medieval martial aspects

Mount & Blade makes for a nice game of the martial aspects of living around 1250. It is commonly regarded as one of the best representations of fighting in that era (Yes, it has a lot of flaws, for instance plate armour and zweihanders, but you could just steer clear of those, and frankly, there is little choice in games)
There is a level-based trial (you can get to lvl 8 before you need to buy the game)

It is a small turkish company that can compete with the big ones, even if only in this specific niche. I can also reccomend the fanbase with its mods. When you find horseriding too easy, try infantry for a big jump in difficulty (and to see why horseriders get these bonusses)

(as a side note, I plowed the rest of the backlog today so you won't see me necroing old posts from now on)