It’s not technically random (that’s why I wrote “more or less”). I meant it more in the common sense meaning of “unpredictable” (which is actually closer to the actual technical definition of random but I digress). Yes, if you look precisely at what’s going on you can exactly determine why postponing lessons on day X lead to no lessons on day X+N, but if you look precisely what’s going on, you can also predict perfectly well what side a die will come up with (it’s just Newtonian mechanics, after all).
And I don’t think what I want is really achievable with the current system. You can go slower, but as soon as you spread out your lessons, you get penalised because will end up stuck on your current level for a few extra days. So you can either go slower or faster than you want to, but not at the actual desired speed.
I don’t mean to sound too negative about this because overall I still think it’s a good system but I think tackling this issue has a chance to make it even better.