GI: Experiments are a dangerous proposition. Valuable resources can be wasted if a creative idea is poorly implemented. At a glance, Valve's 2007 release Portal might have seemed like a risky gamble.
While it came from one of the most respected development houses in the industry, the actual team was small and the gameplay featured novel mechanics difficult to convey in simple screenshots. Even the creators didn't know what to expect from Portal until it released – that's when Valve's experiment turned into a phenomenon.