biased randomness
so if you want to generate "random" numbers but want one number to appear more often, you need modular division.
say I have 0,1,2 and I want 0 the most. what I do is take rnd(4), which gives me 0,1,2,3. now if I take (rnd(4) mod 3), I get 0,1,2,0. the 0 now shows up twice as much as the others. rest in comments
2そうだね プレイ済み