I'm making a simple IOS counting game. It has 3 different worlds with 8 levels in each world. Each level the player will receive stars based on how fast the player completes the level. The player will receive either 1, 2, or 3 stars based on performance. I want these stars to unlock world's 2 and then 3 when the player has collected the amount it takes to unlock the new worlds. Kind of like a Mario game. The levels will be re-playable so the player can get higher stars if they didn't in previous levels.
Two questions now that I'm typing this out.
1: How can I save the stars achieved from completed levels?
2: Let's say a player completes a level, and receives only 1 star and then replays it, and get's 3 stars, I just want to add the newly achieved stars to the star count, how could I do that?