A huge difference is the controls. In CTC you aim by timing the release during the swing of the trebuchet. This is tricky, especially since you can't see the target. In Angry Birds you aim by pointing in the direction you want to launch the bird.

A slight error in the timing of the trebuchet launch easily turns your shot into a complete miss.

Angry Birds does introduce timing later, with the various types of birds whose behavior changes with a tap while in flight, but that generally occurs when the bird is close to the target where a slight error usually doesn't completely waste the bird.

The net result is that in Angry Birds I feel like I'm spending most of my effort concentrating on how best to attack the puzzle of understanding the physics of the level so as to efficiently get through it. In CTC I'm concentrating on the reflex game of clicking at the right point in the trebuchet swing. The former is simply a much more engaging game.

PS: I disagree that CTC is not about killing the people. There are levels with people outside the castle. Take down the castle but leave some of those people alive, and the level is not over. Killing the people is the victory condition, so I'd say the game is about killing the people.

> Killing the people is the victory condition

True, but do you really want to kill those people? They don't even behave like people -- more like "statues that bleed".

> A huge difference is the controls. In CTC you aim by timing the release during the swing of the trebuchet. This is tricky

I'm not so sure. I find operating the trebuchet more intuitive / simple than pulling the sling in the right direction with the right amount of force to send the birds in the air.

BTW, birds fly; they don't need a sling to be airborne... Those "angry birds" are in fact chickens.

Chickens vs. pigs: a simple farm image that speaks to everyone and draws on childhood memories?

The physics puzzle is what attracts most people to the game. But I've noticed with my son the "story" elements, sounds, and characters are also a big draw. He actually wanted an angry birds stuffed animal for Xmas, after seeing the ads on the mobile game.

In addition, for my son I've found that the physics element in Angry Birds has helped build interest in other physics puzzles, including those that don't have as much flavor, such as Ragdoll Blaster.

"Crush the Castle" is associated whith old, slow and boring games with bad graphics. When you see "Angry birds" you wonder "Why are they angry ??!?" and from this point you really want to know.

You got it, and I wonder why nobody mentioned this before. That was my first reaction, too.

Angry Birds also kept its addictive simplicity as the levels increased, which I don't think the OP mentioned. Plants vs Zombies is another addicting game which shows you as a human desperately planting plant shooters in your backyard to defend against invading zombies. The main difference I can feel is that while both games get more difficult as the levels progress, Angry Birds doesn't make it more overwhelming (you still shoot 1 bird at a time at a more complex building with pigs), but PvZ gets super overwhelming with too many plant types to choose from, too many types of zombies, too many factors to manage to the point where my old iTouch lags because there's too many things going on at once. This loses the user in the mess.

Another difference that I haven't seen anyone talk about yet is the fact that while in both games, as you progress, you get different types of ammo, in CTC, you can switch between the different types of ammo at will, while in angry birds, you're stuck with the ammo types you're given, in the order they're given.

While this reduces complexity in Angry Birds, it also means you can't always choose the most devastating ammo, which adds a bit to the challenge.

While your point is very good and valid, it was the article's goal to focus exclusively on the interface, that is why it doesn't mention the story.