Try. You can use it over web, but I feel that the best way is to use the iPhone app.
Definitely unusual, and although it may be too early for me to label it effective (It's just my third day of learning Spanish using DuoLingo iPhone app; I am loving it so far.), based on the reviews and articles that I have read about this app, this appears to be quite effective. In fact, a recent study found this to be more effective than other traditional methods:
Try it! Certainly, a better use of your free time thanor