From the Designer's Website:
Lutte contre les cauchemars.
User Translation from French:
Battle against the nightmares.
("Somnambules" is French for "Sleepwalkers".)
Characters have 4 points to distribute between two attributes: réalité (reality) and rêve (dream). Each point in an attribute gives a specialism relating to that attribute.
Task resolution is performed by rolling a number of six-sided dice equal to the appropriate attribute value, keeping the single best die roll. To this roll, add 2 if a double was rolled, 3 if a triple was rolled, etc. (regardless of whether these were of the same value as the highest die roll or not). Additionally add a further 1 if the character has a relevant specialism. If the result is equal to or higher than a target difficulty number (or an opponent's result if in an opposed action) then the character is successful.