Accomplish the indicated achievement to get the corresponding number of Gamerscore points:

Still Broken (25 points): Save the first continent.
Looking Better (25 points): Save the second continent.
Still a Jigsaw Puzzle (25 points): Save the third continent.
Picking Up the Pieces (25 points): Save the fourth continent.
Almost There (25 points): Save the fifth continent.
One More to Go (25 points): Save the sixth continent.
World Savior (100 points): Complete the game.
Partly Cloudy (30 points): Collect Sun Medals.
Sunny (50 points): Collect all of the Sun Medals.
Half Moon (30 points): Collect Moon Medals.
Full Moon (50 points): Collect all of the Moon Medals.
Blue Streak (30 points): Create an unbeatable Hedgehog.
Power Overwhelming (30 points): Create an unbeatable Werehog.
Getting the Hang of Things (15 points): Get a high score with Sonic the Hedgehog.
Creature of the Night (15 points): Get a high score with Sonic the Werehog.
Helping Hand (20 points): Help someone in need.
Lay the Smackdown (10 points): Improve your Stomp.
Wall Crawler (10 points): Improve your Wall Jump.
Airdevil (10 points): Improve your Air Boost.
Hyperdrive (10 points): Improve your Lightspeed Dash.
Basher (10 points): Get your Werehog level up.
Smasher (10 points): Get your Werehog level up some more.
Crasher (10 points): Get your Werehog level up even higher.
Thrasher (10 points): Get your Werehog level way up there.
Social Butterfly (30 points): Talk to people around the world.
Hungry Hungry Hedgehog (30 points): Eat everything in the world.
Ace Pilot (20 points): Pull off some flawless flying.
Day Tripper (20 points): Race through all stages.
Hard Day’s Night (20 points): Blast through all stages.
Get on the Exorcise Bandwagon (20 points): Drive dark spirits away.
Gyro with Relish (10 points): Eat all the hot dogs in Apotos.
Pig in a Blanket (10 points): Eat all the hot dogs in Spagonia.
Exotic Toppings (10 points): Eat all the hot dogs in Mazuri.
Sausage Fried Rice (10 points): Eat all the hot dogs in Chun-nan.
Iced Hotdog (10 points): Eat all the hot dogs in Holoska.
Kebab on a Bun (10 points): Eat all the hot dogs in Shamar.
Ketchup and Mustard (10 points): Eat all the hot dogs in Empire City.
Hard Boiled (10 points): Eat all the hot dogs in Eggmanland.
Fried Clam Roll (10 points): Eat all the hot dogs in Adabat.
First Time Customer (10 points): Buy something from Wentos.
Oh, You Shouldn't Have! (10 points): Give a souvenir to the Professor.
That's Enough, Seriously (20 points): Give every souvenir to the Professor.
Hedgehunk (5 points): Talk with people in the pursuit of love.
I Ain't Afraid of No Ghost (5 points): Someone is dealing with spectral troubles.
BFFs (20 points): Become better friends with Chip.
Speeding Ticket (20 points): Become the fastest thing alive.
Combo King (20 points): Work on your combos.
Ring Leader (20 points): Gather Rings from all over the world.
Knockout Brawler (20 points): Smash, smash, and smash some more.
Blue Meteor (20 points): Dash through the white walls at top speed.