Exploring Valve Archive, part 17. valvearchive.com>archive>Portal>Portal 2>Art>Boxart Concepts> Because there's so many boxart concepts, I've instead put them all together in a tier list (those are still popular... right???) Portal 2's boxart went through a lot of different iterations. A lot of thought and experimentation went into the design, which was evident from the sheer amount of boxart designs conceptualised. The final art provides iconic imagery and a sense of 'serious whimsicality', but it's fun to imagine what could have been...
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I think the "box art concepts" from your "Wtf is this?" section, refer to the phrase "Now you're thinking with portals"