Defuse: Amalgamated Research Group
From a devious team of developers comes Defuse: Amalgamated Research Groups, a challenging test of your puzzling and mathematical skills. How puzzling? Well, it was also created with help from the folks at the XKCD forums (parental warning: some material at the follow link may not be suitable for young children) which should be a big fat red flag to you right now. What do you need to do? That's simple. Just sign this waiver and I'll tell you.
Suspicious? What? Man, that's crazy. You're crazy. This is a completely legitimate offer that isn't sinister at all. All you need to do is use your mouse to complete a series of challenges in various rooms. Typically, your goal is to light up one square and leave the other unlit by different methods. If you fail? That's... not important. We're sure it won't come to that. But if you should fail, you can just try again. And again. Luckily, the promise of the ultimate reward (which is to say, some light refreshment) is waiting for you at the end, and that should be all the incentive you need. Just remember to keep an eye on the timer. Letting the timer run out would be... unwise.
While light on presentation, Defuse is a snarky, well designed workout for your gray matter. The sparse design doesn't allow for much other than the series of increasingly tricky puzzles on offer, and the timer only adds to the pressure. The lack of any bells and whistles to break up the puzzle solving may deter gamers looking for something lighter to play with, especially considering the lack of any real instruction, but players who enjoy logic puzzles will find the perfect little package to bat their brains against. If you've been scoffing and polishing your monocle at every other puzzle game on offer, Defuse: Amalgamated Research Group may just offer a bit of challenge for you.
Don't forget to sign the waiver.