What's the "unlock code" function under the keyboard icon when buying birdcoins?

[Alan]

What is function of “unlock code” under the keyboard icon when buying birdcoins? I assume its for coins…better yet where do u get free ones/PUs (other than the measly couple a day in exchange of torture by lame ads…

Topic

[NCroc709]

This is for voucher codes that comes with certain Angry Birds merchandise, though none exist for ABF as far as I know. When entered, it will give you free coins, power-ups, or other goodies.
There was a promotional code that was usable in most Angry Birds games during the 5th anniversary of franchise, but I don’t know if ABF had any other codes.

[massiveredlight]

I use codes, comes with soft drinks. Got 20 power potions everytime.
But it works only on PC. Tablet’s virtual in-app keyboard didn’t have “-” key.