[_ea1k]

They were based on skill, but you could also note that the skill requirements varied in ways that were designed to encourage even unskilled players to feel like they could advance with "just one more".

I get your point about the addition of randomness, though. Its an interesting element and it does change things relative to the arcade scenario. Personally, I think that it is largely there to make the system not feel as much like pay-to-win as it actually is.