Angry Birds is an artillery simulator/Puzzle Game. The premise of the game is that some evil, egg-munching pigs have raided the nests of some birds who mean to get their eggs back, whatever it takes. Said egg retrieving involves launching the birds from a slingshot at the pigs, who are protected behind elaborate obstacles of wood, ice and stone. It's a simple concept, but the execution is often anything but easy.There are several different types of birds, most of which have a special ability activated by tapping the screen in mid-flight:
Hal (green toucan) acts like a boomerang, reversing direction and speeding up.
Terence (large red) is slow but, on impact, will either cause a lot of damage or move a lot of blocks.
Bubbles (orange) is small, but puffs up into a larger size if you tap the screen, pushing everything around him out of the way. He deflates after a short while.
Stella (pink) releases bubbles that lift objects into the air and then drop them when the bubbles pop.
The Mighty Eagle is an enormous bird who will wipe out all the pigs in a level. Unlike the other birds, it incurs a one-time activation fee. Unlike the other birds, using the Eagle is a challenge mode, as instead of points you're awarded a percentage score based on how much of the level is destroyed.
The "Year of the Dragon" episode of Seasons introduces the Mighty Dragon which does the same thing as the Eagle but by spinning.
The "Philadelphia Eagles" edition for Facebook introduces a version of the Mighty Eagle known as the "Mighty Philadelphia Eagle".
The Rio version adds Blu and Jewel as special birds in some levels, in two different versions: Chained Heat, where they fly straight forward with a large impact, and Blu alone, who flails around madly after landing or tapping.
Space gives the regular birds a slightly Darker and Edgier makeover (seen as they pass through the space warp in the backstory animation) and changes some of the colours. In particular, Terence becomes green, the Mighty Eagle becomes a Space Eagle that wipes out everything around the launched fish tin instead of killing every pig, and Chuck becomes purple and will travel at high speed towards whatever point you touch on the screen. The game introduces a completely new light blue bird shaped like an ice cube that freezes all items around it, making them easily smashed by the Blues. The summer 2012 update introduced bonus levels in which you fire eggs that hatch into mini-black holes, which don't do much damage themselves but which you have to use to attract pigs and scenery so that they smash into each other.
Both AB Star Wars and AB Transformers not only have the birds cast as characters from the films, they have character-appropriate abilities (lightsabers, Force pushes, blasters, electricity, Force lightning, and others).
The Puzzle Game aspect (and the game's main source of difficulty) revolves around the best use of the available birds in each level to collapse the obstacles onto the pigs, as all the pigs have to be taken out to win a level. Scoring per level is based on pigs killednote 5000 points per pig, damage done to the obstacles, and the number of birds left over at the end of the levelnote 10000 points per bird, with 1 to 3 stars awarded upon completion based on all of the scoring factors as well as points. In some levels, it's more important to finish using as few birds as possible; in others, it's a matter of causing as much destruction as you can. Achievements can also be earned for finishing episodes, three-starring all levels in an episode, scoring a certain number of points in an episode, and other things. Each episode also includes a number of hidden Golden Eggs which, when found, open bonus levels.The game in the series so far:
Angry Birds Seasons, featuring (mostly) holiday-themed episodes. The first Season contains episodes for Halloween, Christmas, Valentine's Day, Saint Patrick's Day, Easter, summer, and the Chinese Mid-Autumn Festival. The second Season has new Halloween and Christmas episodes, as well as episodes themed after the Chinese New Year, Cherry Blossoms, Atlantis, and "back-to-school". The third Season has new Halloween and Christmas episodes and one themed around a fair. The fourth Season only has a new Christmas episode to date.
Angry Birds Star Wars, a sequel / Crossover with the original Star Wars film trilogy. Unlike Angry Birds Rio, which featured the normal birds alongside the cast of Rio, this game utilizes the Universal-Adaptor Cast trope, with birds and pigs alike portraying the various characters.
Angry Birds Star Wars II revolves around the prequel trilogy, and allows you to play "light side" and "pork side" routes with corresponding characters.
Angry Birds Friends, which connects to the Facebook version of the same name and lets you compete in a weekly tournament. Most of the original gang is present. For tournament levels, the eagle is replaced by the superhero themed Wingman.
Artillery Game: In a loose sense of the term — the slingshot controls your launch angle and speed, each bird leaves a visible shot trail, and the goal is to eliminate your opposition (either through direct hits or, more often, collateral damage). But the pigs aren't actively aiming and shooting at the birds in return, (except in the Star Wars version)and you only have a limited number of birds to take out the pigs with.
Subverted in some bonus levels which are built around chain reactions; there's a random chance that the mechanism does partially fail, and some of these can be failed completely if you don't shoot a bird properly to trigger the chain reaction.
Autosave: The games automatically save your progress every time you complete a level.
Level 4-15 is a battle against Nigel, who appears twice more in cameos, one to send marmosets out against the birds, and the other to capture Jewel and Blu. He reappears again in level 12-15 for the climactic battle.
Level 8-15 is a fight against the marmoset leader, who jumps around on platforms. He shows up again in level 14-15.
In AB Space:
The final levels of the first two planets in have boss battles against the King Pig in a tank-like contraption and flying saucer, respectively.
The fourth planet has a boss battle against a pig so large, it generates its own gravitational field.
You have to fight Lard Vader in the final levels of the Death Star and Cloud City episodes in AB Star Wars, and both he and the Emperor at the end of the second Death Star level.
In AB Space, you can earn Space Eagles for completing the first two planets; once you run out, you have to buy them. (Or you can just leave the game and come back later to "earn" one.)
In both Angry Birds Friends (the Facebook app) and the latest release for the main game (2.2.0), you are able to purchase "power-ups" for use in-game. The power-ups include: Super Seeds (makes the bird grow larger), the King Sling (super-powered slingshot), Sling Scope (you can see the flight path before launch), and Birdquake (an earthquake occurs). However, you can earn bird coins each day and potentially avoid having to spend real money (though the option is there)
In AB Star Wars, you can either pay $1.99 to upgrade Luke's lightsaber to the green version (slightly longer and more powerful), or you can finish the entire 40-level Dagobah-themed "Path of the Jedi" episode.
The "Red's Mighty Feathers" episode in the original game is one with Bad Piggies, as Red tries to bust the pigs' various contraptions to keep them from making off with an egg.
AB Rio is one with the film, as the poachers capture the birds, who escape and set out to rescue Blu and Jewel. Subsequent levels are set in the movie's Rio de Janiero and have the birds targeting the marmosets instead of the usual pigs. Blu and Jewel are also available as ammunition in some levels.
Cross-Popping Veins: Red sports one in the first panel of the opening comic for the "Red's Mighty Feathers" episode.
Wingman in the tournament. At least you can get him for free with enough bird coins.
The Millenium Falcon in Star Wars.
Disaster Dominoes: Several levels can only be solved by causing collapses at strategic points that trigger additional collapses. On the other hand, hit the wrong spot and some of the pigs will be too well protected by fallen rubble.
The trailers often show how disproportionate the birds are to insects who merely touch, much less tip over, their eggs.
If you think more about the level design, you'll realise the birds are destroying a jarring number of civilian buildings, including carousels (with small pigs clearly representing kids), buses, airplanes, schools, fishing events, and giant plates of food. When counting pig casualties, you may start wondering why those birds aren't labeled as terrorists.
If you fail a level, the remaining pigs do this as the last bird disappears and the "Level Failed" screen comes up. Even the pigs' grunting while you're playing a level sounds like laughter at times.
Nigel does this in Rio if you flub a shot, and in the "level failed" screen. If you fail a level populated with only marmosets, you get a dancing marmoset thumbing his nose at you and screeching, which sounds like laughter.
An animated pig in an air bubble does this on the "level failed" screen in AB Space.
Lard Vader laughs at you on the "level failed" screen in AB Star Wars. In AB Star Wars 2, it's Lard Sidious.
In the game's fluff, the other birds are terrified of the Mighty Eagle and offer it a can of fish as payment for fighting the pigs. In-game, when you use the Eagle, a can of fish appears by the slingshot (replacing any unlaunched birds) which you launch at the pigs; the Eagle comes zooming in and lands on or near the can. See the trailer here.
The Mighty Dragon from Seasons is a bit more jovial, but still has to be convinced to help via a fresh golden fish.
Follow the Leader: To truckloads of artillery games, and followed by plenty of imitators itself.
Friendly Fireproof: Subverted. The birds can't hurt each other, either through impacts or special attacks. However, a bird that's stunned or jumping into the slingshot will knock out a launched bird, so carefully timing launches and waiting until the bird(s) poof out from where you want to aim are generally good ideas.
In at least one level, a bird could get stuck and refuse to disappear. 
Be careful if you're running an old version on XP, because an update glitch can not only crash the game but curse it unto the seventh generation, to the point where uninstalling and reinstalling will not let you run the game.
This is a game mechanic in both Space and Star Wars, as all the planets in Space and some areas in Star Wars have a gravitational "bubble" that not only pulls the birds toward them, but can also pull floating pigs to the ground to be eliminated if they're pushed inside it. It also affects how everything falls once a bird hits something, as objects will scoot/roll around the planet in the direction they fall until their momentum runs out.
Chuck's ability zigzags the trope in Space. Gravity affects him as long as he's just flying or after he hits something, but his speed boost makes him immune to gravity. Boba and Jango Fett's abilities in the Star Wars games also do the same.
Hair Trigger Explosive: If a bird, rock, piece of wood (anything, really) hits a box of TNT, it will blow up (even if there's no source of fire).
Harmless Villain: The Bad Piggies. Even when they're under attack, all they do is stand around. Some are even floating aimlessly in Angry Birds Space, and many times, the pigs are sleeping as long as there's not a bird near them. They have no means of fighting back or harming the birds.
In AB Star Wars II, you can play the Pork Side route, which shows the films' events from the bad guys' perspective and lets you play using the evil characters. The option is available in the first route but has to be unlocked for subsequent routes.
Not Quite Dead: The King Pig. No matter how many times he gets killed in the game, he (or is that another King Pig?) is rough and ready for another round.
Oh Crap: In Space and Star Wars, the pigs look scared when a bird or debris gets close to them. One of the possible scoring achievements in Space is to scare at least 6 pigs with one bird.
One Bird Completion: In many stages across the franchise, you will only get three stars in a level if you complete it with the first bird.
Put the "Laughter" in "Slaughter": Not only do the birds laugh and cheer when you complete a level, several of the birds sound like they're laughing when you draw back on the slingshot, and yell delightfully as they're launched.
All of the theme tunes for the various episodes of Seasons are holiday-appropriate reworkings of the original's theme (for example, Christmas carols for the Christmas episodes, creepy organ for Halloween, an early-sixties rock'n'roll pastiche for "Back to School").
"Rio" used a samba rearrangement of the theme.
"Space" has a bombastic John Williams-style arrangement for the main theme, and SF atmospheric background sounds.
"Star Wars" and "Star Wars 2" use a reworking of the traditional Star Wars theme that follows the Angry Birds theme's meter.
And now, the original game itself has gotten its theme remixed.
Level 17 of the "Summer Pignic" episode is a space-themed level which is set on the moon; the obstacles resemble a lunar lander and a moon car. It was released on July 8, 2011, the date of the final launch of the space shuttle Atlantis, which was also the final launch of the space shuttle program.
Too Dumb to Live: The pigs don't fight back in any way as a game mechanic, but more properly, they seem to build the flimsiest possible fortifications and put boulders and TNT boxes all over the place, as if daring the birds to blow them up. Also, they mistook a bubble egg as an actual egg in the Back to School (AB Seasons) trailer. Another thing is that they keep trying to steal the eggs, despite what keeps happening to them.
Useless Useful Spell: The powerups that were introduced in Angry Birds Friends. They seem quite powerful in certain situations if you need a little boost, but don't rely on them too much, because if used at most times, they are worthless.
The volcanic vents in the "Red Planet" level of Space.
There are large air vents in several levels of the Cloud City episode in Star Wars that alter trajectories of both birds and debris. The latter half of the episode introduces moving air vents that make things even more challenging.
Waddling Head: The Bad Piggies. They look like green pig heads (without legs), but they do leave pig hoof-prints behind.
Watch the trailer introducing Al: the pig in the hat also wears sandals, despite having no visible feet.
What Measure Is a Non-Cute?: The King Pig, no matter how evil and obnoxious he may be, still has an air of amusing adorableness in him. Whether that works is up to you.
Christmas Episode: One in each "season", all themed like Advent calendars in that each level is only unlocked 24 hours after the previous one. In the first, the birds tear up over the Christmas Star.
Our Dragons Are Different: The Mighty Dragon resembles a traditional Chinese dragon with a long, serpentine body and antler-like horns, though his head is shaped suspiciously like that of the Mighty Eagle.
Tertiary Sexual Characteristics: The female birds and pigs in the Valentine's Day episode...which gets weird in retrospect now that it's been confirmed that White Bird has always been a girl but lacks these characteristics.
Specific to Angry Birds Rio
Brick Joke: When the birds first get abducted, their eggs are left behind. At the end of the game, the pigs appear and are about to eat the eggs when the birds crash the plane on top of them.
Chuck Cunningham Syndrome: Matilda has strangely been left out of Space. Notable because she is one of the five original members of the Flock. Worse, she is also always absent in the trailers, with the reason of her unpopularity unknown.
Empathic Environment: The planet-sized alien fish in the "Pig Dipper" episode will react to your moves, looking surprised or angry as debris, pigs, and birds land on them.
Flying Saucer: The King Pig flies around in one. Some of the normal pigs can also be found in structures made to look like one.
An Ice Person: The blue cuboid bird freezes solid everything in its blast radius as its special ability. This can often take out pigs immediately, and makes things like wood and stone brittle enough that blue birds can shatter them easily.
Nuclear Nasty: In the "Beak Impact" episode, rocks with radioactivity signs can shatter and create bubbles of radioactivity (complete with Geiger counter clicking) that turn pigs into bloated, three-eyed monsters before popping them.
Product Placement /Loophole Abuse: What do you mean, NASA couldn't legally advertise? Unless Rovio asked them of course. The "Red Planet" and "Beak Impact" episodes are based on NASA's Mars programme and the proposed Asteroid Retrieval Mission. Eggs are replaced with various NASA spacecrafts.
Role Reprisal: Played with for fun as Ian McDiarmid, the original actor who played Emperor Palpatine on Return of the Jedi and the prequels, voices the pig version of Emperor Palpatine.
Spread Shot: Once Lando takes over for Han in the latter half of the Cloud City episode, his blaster fires a 3-bolt spread instead of 3 shots in a straight line. Captain Panaka in AB Star Wars 2 shoots two 3-bolt spreads instead of just one.
See also the stormtroopers, who spread fire in every direction but where you aimed.
In the first game: Luke is the red bird. Obi-wan is the black bird. Chewbacca is the big red bird. Both Han and Lando are the yellow bird, colored appropriately. Leia is the pink bird. C-3PO is the white bird. R2-D2 is an egg.
In the second game: Qui-Gon (an eagle) takes over for Luke as the lightsaber bird. Obi-wan, C-3PO, and R2-D2 are unchanged, Obi-wan's younger appearance aside. The red bird is now Anakin from The Phantom Menace, mimicking the Jewel/Blu Chained Heat dynamic with his special ability. Jar Jar gets Leia's "grab stuff from afar" ability, only it's with his tongue. Zam Wesell also has this ability, using a grappling hook. The pink bird is now Padme, whose beams push their targets instead of pulling them. Captain Panaka is the yellow bird (although he's brown) and has Han/Lando's blaster ability. Count Dooku gets the green bird's boomerang ability (and, since he's a pig, is green himself), but it's with his lightsaber instead of himself.
YouTube can be your best friend if you're stuck on a level. There are also multiple websites, such as angrybirdsnest.com, dedicated to showing runthroughs of levels.
Finding the golden eggs. Here are some of the more nonsensical ways to get them:
Tapping the sun on the level select screen.
Tapping the treasure chest on Level 1-8. The word "chest" will have to be typed in on the PC and Mac versions afterwards.
Selecting "Danger Above", then scrolling the screen all the way to the left.
Launching Matilda backwards, then tapping the screen so that Matilda "jumps" and hits the middle of the pause button.
The Merch: In many kinds, but especially the line of plush Angry Birds (which range from keychain-size to softball size), which includes the Rio characters, and several have electronic game sounds. And are safe enough to throw at things!
100% Completion: Getting all three stars on every level up to and including Birdday Party (on iOS) or Surf 'n' Turf (on Android) in Angry Birds will unlock a golden King Pig face on the Golden Eggs menunote Alternatively, you can buy a King Pig figure from Mattel's Apptivity toyline and use it on the iPad version to unlock it. Touching it will take you to a random level of the game, with a special random game mode in effect. Scoring Points is completely averted at this point. These game modes are:
Remixed Level: Material Mix Up! — Two types of materials in the pigs' structures have been swapped, affecting the level's difficulty in some way.
Silliness Switch: King Pig — The pigs are replaced with eggs, and the birds themselves are replaced with pigs. Each bird is reinterpretated as a pig with its special ability retained in some way.
Timed Mission: Bird Frenzy! — You are given a limited amount of time to complete the level with unlimited, but randomized, birds.
Unexpected Gameplay Change: Total Destruction! — Again, you have limited time, but this time you can simply tap anywhere to create an explosion.
Opening the Sandbox: In the first game, you can't play any of the other episodes until you clear the first one. This is averted as of the Birdday Party update, which unlocks all episodes by default.
Real Life Writes the Plot: During the game's development, the developers decided that the birds needed an enemy once the game had been developed enough. At the time, the "swine flu" epidemic was taking the media by storm. Now you know why the birds' enemies are pigs.