 Within the first week of this offer, over 1.5 million copies of the game were downloaded through Steam.A similar promotion was held in September 2011, near the start of a traditional school year, encouraging the use of the game as an educational tool for science and mathematics.Valve wrote that they felt that "Portal" "makes physics, math, logic, spatial reasoning, probability, and problem-solving interesting, cool, and fun", a necessary feature to draw children into learning.