Achievements
     Complete each achievement to get the allotted gamerscore.
Note:  The achivements are not achievable in splitscreen.

Acrobat (40):            Perform a two stunt combo.

Adrenaline Junkie (40):  Stay in adrenaline mode for 30 seconds.

Backflip (25):           Perform a backflip.

Berzerk (50):            Take down three opponents in a row without 
                         crashing.

Big Air (25):            Stay airborne for 3 seconds.

Boostaholic (60):        Stay in adrenaline mode for 60 seconds.

Bully (30):              Take down one opponent.

Crowdsurfing (40):       Collide with the spectators.

Double Backflip (50):    Perform a double backflip.

Double Frontflip (50):   Perform a double frontflip.

Frontflip (25):          Perform a frontflip.

Frozen (50):             Hold a stunt for 4 seconds.

Hangtime (25):           Hold a stunt for 2 seconds.

HeadSplat (60):          Land on top of another player.

Hoarder (30):            Unlock half of all unlockables in career mode.

Orbit (50):              Stay airborne for 5 seconds.

Pack Rat (50):           Unlock all unlockables in career mode.

Rampage (70):            Take down four opponents in a row 
                         without crashing.

Roadrunner (40):         Lead a race from start to finish.

Stingy (30):             Collect $50000 in career mode 
                         without spending them.

Untouchable (60):        Win a career race with your sled intact.

Wire Fu (60):            Perform a three stunt combo.

Woodcutter (40):         Collide with 3 trees in a race.