If You complete the indicated task You'll get the allotted gamerscore.
The Per Lundberg syndrome (30) - Get 100% of all medals.
Incognito (25) - In single player, clear each standard level collecting less than 20 points.
Hard as Rock (25) - Complete the game on Hard difficulty.
Given to wail (20) - Clear all levels using a guitar.
Stabilized (15) - Get all medals in any level.
Skull and crushed bones (15) - Crush 10 skulls without touching the ground.
Bubbler of the week (15) - Get 10 enemies within the same bubble.
Firewalker (15) - Defeat 100 enemies using the Fire Boots.
All powered up (15) - Have all 4 power-ups at the same time.
Ambitiously ambidextrous (15) - Clear at least 3 levels with all 3 controller types.
Ready to rock (5) - Clear the first level.