- Singing turrets
There is a turret inside a ventilation grate just past the elevator in Test Chamber 16. Jump over it, get the Refraction Cube, then use the laser to destroy that turret to open the grate. Enter the new area to find four turrets singing a song.

- Alternate title screen
Successfully complete the game to change the title screen.

- Avatar Awards
Successfully complete the indicated task to unlock the corresponding Avatar Award:

Love Shirt	Hug 3 friends in Portal 2 Co-op mode.
Portal 2 Hat	Survive the manual override.
Companion Cube	Successfully complete Portal 2 in Single Player mode.
Portal 2 T-Shirt	Successfully complete Portal 2 in Co-op mode.
Turret T-Shirt	Successfully complete Test Chamber 10 in under 70 seconds.

- Achievements
Do the following things to obtain the corresponding Gamerscore points:

5 Points
Pturretdactyl	Use an Aerial Faith Plate to launch a turret.
Good Listener	Take GLaDOS' escape advice.
You Monster	Reunite with GLaDOS.
High Five	Celebrate your cooperative calibration success.
Scanned Alone	Stand in a defective turret detector.
Wake Up Call	Survive the manual override.
10 Points
You Made Your Point	Refuse to solve the first test in Chapter 8.
No Hard Feelings	Save a turret from redemption.
Undiscouraged	Finish the first Thermal Discouragement Beam test.
Bridge Over Troubling Water	Finish the first Hard Light Bridge test.
Can't Touch This	Dance in front of a turret blocked by a hard light bridge in co-op.
Asking for Trouble	Taunt GLaDOS in front of a camera in each of the five co-op courses.
Confidence Building	Finish all test chambers in the Mass and Velocity co-op course.
Team Building	Finish all test chambers in the Team Building co-op course.
SaBOTour	Make a break for it.
Portrait of a Lady	Find a hidden portrait.
Ship Overboard	Discover the missing experiment.
15 Points
Tater Tote	Carry science forward.
Tunnel of Funnel	Master the Excursion Funnel.
Still Alive	Finish Course 4 with neither you nor your co-op partner dying.
Vertically Unchallenged	Master the Repulsion Gel.
Gesticul-8	Perform all 8 gestures of your own volition in co-op.
Dual Pit Experiment	Do the same test twice.
Stranger Than Friction	Master the Propulsion Gel.
White Out	Finish the first Conversion Gel test.
Bridge Building	Finish all test chambers in the Hard-Light Surfaces co-op course.
Stalemate Associate	Push the button!.
Triple Crown	Solve 3 co-op chambers in the Mass and Velocity course in under 60 seconds each.
Obstacle Building	Finish all test chambers in the Excursion Funnels co-op course.
20 Points
Lunacy	That just happened.
Rock Portal Scissors	Be victorious in 3 co-op games of rock-paper-scissors sequentially.
Iron Grip	Never lose a cube in Chamber 6 of the Mass and Velocity co-op course.
Door Prize	Examine all the vitrified test chamber doors.
Schrodinger's Catch	Catch a blue-painted box before it touches the ground.
Portal Conservation Society	Finish Chamber 3 in the Hard-Light Surfaces co-op course using only 5 total portal placements.
Air Show	Perform 2 aerial gestures before touching the ground in co-op.
Preservation of Mass	Break the rules in Test Chamber 07.
Final Transmission	Find the hidden signal in one of the Rat Man's dens.
Drop Box	Place a cube on a button without touching the cube.
The Part Where He Kills You	This is that part.
25 Points
Party of Three	Find the hidden companion cube in co-op test chamber.
Four Ring Circus	Enter 4 different portals without touching the ground in co-op.
Narbacular Drop	Place a portal under your co-op partner while they are gesturing.
Empty Gesture	Drop your co-op partner in goo while they are gesturing by removing the bridge under them.
30 Points
Overclocker	Finish Test Chamber 10 in 70 seconds.
Pit Boss	Show that pit who's boss.
50 Points
Friends List With Benefits	While playing co-op, hug 3 different people on your friends list.
75 Points
Professor Portal	After completing co-op, complete Calibration Course online with a friend who hasnâ??t played before.
Smash TV	Break 11 test chamber monitors.
100 Points
You Saved Science	Finish all test chambers in all courses of co-op.

- Bonus store items
Successfully complete the indicated task to unlock the corresponding item for purchase at the store:

Bionic Beanie	Successfully complete 'Lunacy'.
WCC Flag	Successfully complete 'High Five'.

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