Sega's Sonic the Hedgehog YouTube channel this weekend held an Extra Life charity livestream to help raise money to benefit the Children’s Miracle Network - a network of 170 non-profit children’s hospitals throughout the United States and Canada.

As part of this, there was a series of milestones throughout the stream, where viewers could unlock never-before-seen Sonic Adventure and Sonic Heroes concept art. In the end, all milestones were unlocked! Take a look at each one below:

Sonic Adventure 2 concept art
Image: Sega
Sonic Adventure concept art
Image: Sega
Sonic Adventure concept art
Image: Sega
Sonic Adventure 2 concept art
Image: Sega
Sonic Heroes concept art
Image: Sega
Sonic Heroes concept art
Image: Sega

The final milestone unlocked some early demo versions of four Sonic Adventure 2 music tracks, which were provided by Jun Senoue. These include beta tracks for City Escape, Mission Street, Metal Harbor and Radical Highway (thanks, Tails' Channel).

Are you a fan of any of these Sonic games? What do you think of the above concept art and music tracks? Tell us below.

[source tailschannel.com]