OSR 1 Gp vs 1xp?

[Mannahnin]

I don't remember who wrote it or where I found it, but I remember an RPG that had an interesting mechanic for spending XP. Instead of gaining levels, you spent your XP to "buy" things like feats, hit dice, and skill proficiencies. Like, if you wanted an extra d6 of sneak attack damage, you could spend 2,000xp for it...if you wanted another spell slot, they were 1,000xp per level. Or something like that.

I thought it was an interesting way to do a "level-less" RPG.

The TSR Marvel Super Heroes game did something similar. Heroes accumulated Karma points, which could be spent in a pinch to adjust rolls on the % resolution table, or could also be saved up to increase attributes, powers, or invent new "power stunts", special ways of using your superpowers. If you killed someone you lost all your unspent Karma, which was a pretty good incentive to heroic play.