ok, we finally found that wretched (almost invisible) button and the coffin opened, yay !
now, we came to the room with blue circles. is it possible to cross to the other side ? there is a colour code at the back of pyramid but we can't understand how it could possibly relate to it and help us find the path to to the other side ? only one bright green entrance out of 3 is working and from there we can reach 1st blue circle but then neither straight nor left is working. so how ?