Hint: 100%:
In order to get 100% at the game select menu you have to find a secret lums in the Tomb of the Ancients level. In the first part of the level, after having activated the 3 switches that raise the platforms in the poisonous pond, jump on these floating platforms and climb the web on the other side. Once at the top, instead of just falling down the pit, place yourself at the edge of the wall, to the left (when facing the poisonous pond), Then, fly over the pond, go as far to the left as possible to find a narrow hall in the wall, and land on the platform. Follow this path and kill some pirates to get the 1000th lums in the skull's eye.