You can also build your own levels from scratch, but even that's not the best part. The
best part is the way you can share levels with your friends. No need for Nintendo Wi-Fi. No need for DS codes. Okay, so I'm easily impressed by
science and technology, but I think you guys will think this is very, very cool.
You can save the levels you make as sound files, just like the way old data cassettes used to do. When you save a level, it makes a sort of rush-and-whirr sound the way a modem does. You can record it to your PC, save it as a Windows media file or whatever you want, and then put it on a website or email it to a buddy. Anyone who downloads the sound file simply plays it into their DS microphone, and voilà - your friend now has the level you made.
If your friend is with you, of course, you just play your sound file on your DS directly into your friend's mic. I know that this is actually ancient technology, but I was totally dazzled to see it repurposed like this. The wonders of human advancement!