The next two additions are a real joy to behold - and offer a whole new dimension to the Portal world by allowing you to change the properties of surfaces. The bright blue Repulsion Gel creates big bouncy puddles you can use as a trampoline, whilst Propulsion Gel is an orange gunk that transforms flooring into a super-slippy slide.
(Valve accompanied this with the a rather fun, rather infantile 'whiz' noise, suggesting its toddler-pleasing qualities won't be ignored in-game).
Valve's final chunk of evolution comes in two-player co-op, which we're promised will arrive both in split-screen and online.
Graphically, it looks brilliant - with Valve using the 'lab gone wild' premise to shoehorn in a lot more colour and arresting architecture than the first game's rather bare locales.
With all these new additions, it appears that Portal 2's arrival on PS3 might not be the biggest story behind the game after all. Despite Valve very noticeably showing us our demo on a Blu-ray disc.
"We're a lot alike, you and I," GlaDOS tells us during our demo. "You tested me, I tested you. You killed me, I... oh wait. I guess I haven't killed you yet. Hmm. Food for thought."
Bring it on, love.