cocos2d

First time really trying to get something done in iPhone SDK. After struggling ages getting a simple game loop to work - only to discover that I was calling the update routines on the wrong thread - I found a forum post which talked about the cocos2d iPhone 2D game engine.

Have now spent most of the day working on a simple Memory-like game. The engine is pretty straight forward to use once you get to know the APIs. There are a couple of things I didn't quite figure out this time, though - any insights are appreciated:

1. Is there any reason why rendering origin in iPhone / cocos2d / OpenGL seems to be lower left corner instead of upper left? It sure matches the mathematical way of thinking about an origin but AFAIR most of the other frameworks have their origin in the upper left, don't they?
2. To render the game board, I have assembled a Scene using a Layer and a couple of Sprites contained in that Layer where each of the Sprites was supposed to be touchable. I haven't found a way to get that working other than reacting to touches on the Layer and manually checking whether the touch fell within the bounds of one of the Sprites. There must be a better way to do this, right?
3. How does memory management work when you replace Scenes using the Director singleton? You access the Scenes via [Scene node]; so I assume there's autorelease at work.
4. Why do Texture2D.pixelsHigh / .pixelsWide return different values than Texture2D.contentSize?