The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From Knowledge Host:
Reaktions is a free and highly addictive game of speed and intelligence.A simple test of your reactions. In Classic mode, touch the square before it disappears, the further you progress, the less time the square shows.In Advanced mode, not only do you need to use your fast reactions, you need to remember which shapes give you points, which deduct points and which ones end your game straight away. Again, the further you progress the less time you get to react.Whether you play in Classic mode or Advanced mode, you will need to show great speed and memory to build up your score.