Nixie - Challenge Your Brain comes from Andrew Zaharek and Joshua Levesque. It's a free puzzle app game that took me extra time to understand. It's very similar to Akari, which is also known as Lighthouse. I exchanged a few emails with Andrew & learned that he never knew about Akari. Weird: I solved all of the beginner levels, but didn't really understand what I was doing!
There are about 130 levels. I've solved all but 10. Right now I'm stuck on the hardest category #2. It's a massive grid where one must use a certain amount of guess & check.
Something annoying: Nixie is free but there are video ads. They pop up every 3 or 4 levels. Even more annoying, they can pop up when you want to clear the board by clicking refresh. Andrew informed me that they are going to make them less frequent. There's also a time element to them.
Without a doubt, Nixie is the best game of the week and will certainly make the list of Best Puzzle Apps of 2014. It's a pure puzzle.
Great job Andrew!