Why you put fake percentage in the caves !? i am sure the percentages put in caves are fake and the real ones are much lower .
I'm in the 4th cave with   60% chance for stone , 40% for copper , 25% tin and 6% bronze . as you can see there is a very little chance that i get nothing BUT , i mostly get nothing 6~7 times in 10 clicks . i assumed maybe im being unlucky . but math doesnt lie , i have counted about 50 times , and im dead sure percentage you put in the caves are FAKE and lower than what it seems .

one other thing is that i seem to get nothing 4 or 5 times in a row although the percentage is lower than stone , but i dont get Stone more than 2 times in row . there is something very fishy there .
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I can confirm this , i just spend 450 energy and never gotten stone more than 2 times in a row (got 2 times in a row only 4 times) , but got "Nothing" in a row ALOT , highest was 5 times in a row .