Darkness disapear bug ?

[prouve]

Hello

I think i found a bug... When i am about level 45, the Darkness element disapear, i can't chose it ??! so i chose an another element, and then darkness is back...

i tried with 4.2 and 4.2d version... i play always in short mode.. here are my elements chosen..

Interest > Interest > Interest > Light > Fire > Earth > Light level 2 > Fire level 2 > Earth level 2 (and then, impossible to chose darkness...)

i can't build periodic with that bug ^^

thanks

[water_region]

i encountered a similar problem

i chose all the lv1 elements except fire

then i chose light lv2

after the next wood fire lv1 disappeared