http://www.wouldyoukindly.com/portal-2-dlc-coming-this-summer-valve-talks-original-plans-for-prequel/
As soon as I read this, the way the game was made a lot more sense to me. You know, it was disappointing. This thing I'm linking doesn't have the whole story there, but essentially they wanted Portal 2 to be a prequel with completely different gameplay. They were building the whole thing but test audiences just wanted it to be like the first one. Eventually they gave in to these idiots and changed everything. Of course they still wanted it to be new and exciting, so they brought in a number of new gimmicks, but as it was so rushed, these ended up making everything so linear. The game became looking for that one patch of white to make a portal on. Just think of what could have been.
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Kiwi