Once I saw the Portal 2 trailers, something bothered me. Portal 2 uses a few gels to aid in puzzles.  Repulsion Gel & Propulsion Gel, have so far been revealed.
This reminded me of a game I saw on 4/7/2009. That is the day that on the video program CO-OP, had their "Indie Games Special" where they showed off several indie games and their devs. Well, if you watch that video, you will see a game called. TAG: the power of paint.  
 
If you have played the game or seen that episode of CO-OP, you will notice that TAG uses gels or "paint" to apply different effects to the ground. Red for speed. Green for jumps.  Blue to stick to objects.  This just seems alittle strange. 
 
If you would like to read more about "The Power of Paint" go to  https://www.digipen.edu/studentprojects/tag/  (The website given in the episode has since shutdown) And if you'd like to see the Indie Games Special you can download it on itumes or, go here  http://revision3.com/coop/feed/quicktime-high-definition/.
 
Does anyone else find this strange?