Speaking in an exclusive interview with developmag.com, Portal team leader Kim Swift has spoken on the vital importance of playtesting in crafting games.
"Playtesting is so incredibly valuable to the process. We started playtesting Portal literally the week we got [to Valve]. We tried to playtest every week, and every time we'd design a level or a piece of exposition we would try and get it in the game within two to five days, so we could see if our decisions were the right ones."
Swift is keen to not just pin the success on how polished the progression curve was, however - key to the game's enduring popularity, she thinks, is how much fun they had developing it.
"I think essentially we had a ton of fun making the game and I think that gets reflected in the game itself, she adds." People can tell that we had a good time and that we want our players to have a good time too."
For more from Swift, including her opinions of game degrees and the reticence of some studios to hire graduates, check out the full interview here.