Only see a blank screen at launch

Does NOT work on my iMac.
When launching the sound is okay, but screen remains “blank”. Only see the mouse pointer.

iMac (late 2012)
2.7 GHz Intel Core i5
8 GB 1600 MHz DDR3
OSX El Capitan
NVIDIA GeForce GT640M 512MB

Mistymistymistymistymistymisty about realMyst: Masterpiece Edition, v2.0.0