the cyan and purple area should span the whole red area, in the left case the vflex is getting calculated incorrectly
the invisible div between grey and cyan uses ---> sclass="displaynone" FAIL (when the div is empty)
the invisible div between grey and cyan uses ---> sclass="displaynone" OK (when the div is NOT empty)
the invisible div between grey and cyan uses ---> style="displaynone" OK (even if the div is empty)