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Unfortunately, Portal games encourage you to try and break out of their levels, and gels give you a lot of options for that. Easter eggs are generally easy to find but the most entertaining ones will take some creative thinking (probably some noclipping too). The developers clearly put care into their original levels, throwing in plenty of Easter eggs and an alternate ending.
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Occasionally Aperture Tag will revisit a level from Portal 2 and cheerfully let you utterly break it with the new gun. This makes the puzzles generally engaging and reasonably challenging, though there is a drop in difficulty in the middle of the game. When you can paint almost any surface you have to consider the whole environment. Giving you this paint gun helps address what I thought was a negative of Portal 2: towards the end puzzles became a game of "can you spot the white tile". It turns out that there aren't really that many ways you can combine the two gels, but the game doesn't outstay its welcome, and if you're still not satisfied there are community levels available via the Steam Workshop. You won't see any of Portal 2 or TAG's other gels here, but the two gels are enough to make a decent game. Aperture Tag puts the power of Portal 2's repulsion and propulsion gels in your hands, creating a kind of spiritual successor to TAG: The Power of Paint.
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