The size? i think the best is repeat the basic arena x2 or x3 times (only in X axis or Z axis). Or you can forget about different sizes and put...
The size? well i think the easiest way is small (12x22) medium (24x44) big (36x66), with this you only have to add the same "puzzle" in each area...
I think it need that player pay some money to join (and give it back when exit with "/rounds leave") because with this players can gain infinite...
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