Mucking about with noLoop() and loop() and redraw() is not the way to go about it.
Instead, have a variable, state, that keeps track of what state the game is currently in.

Example:

1. int state = -1; // -1 means click to start screen.
2. int endTime;
3. 
   
4. void setup(){
5.   //...
6.   state = -1;
7. }
8. 
   
9. void draw(){
10.   if( state == -1 ){
11.     background(0);
12.     text( "Click to start" ):
13.     // ... etc
14. }
15.  if( state == 0 ){ // state 0 means you're playing the game.
16.   //... Draw balls to click on, etc.
17. }
18. if( state == 1 ){ // state 1 means the game over screen.
19.   background(0);
20.   text( "game over" );
21. }
22. if( state == 0 && endTime < millis() ){
23.   state = 1; 
24. }
25. } // End of draw()
26. 
    
27. void mousePressed(){
28.   if( state == -1 ){
29.      state = 0;
30.      endTime = millis() + 10000;
31. } 
32. if( state == 0 && mouseOnBall() ){
      // .. deal with ball clicked
    }
33. if( state == 1 ){
34.   state = -1;
35. }
36. } // end of mousepressed()

Hi,

Hi again,

That's a classical too...
If the mouse is not on the ball, what your function will return? Nothing there.
One way to fix it is just to add a return true at the end of the function.
Another is to just use the boolean type the right way:

1. boolean mouseOnBall() {
2.   return mouseX >= ballX && mouseX <= ballX +ballDiam &&
3.       mouseY >= ballY && mouseY <=ballY + ballDiam;
4. }

Hello,

I thought a boolean could only return true or false, not a series of logic statements.

Relational operators like <, >, <=, >=, == and !=, along w/ logical operators !, && and ||,
always result in a boolean value. That is, either true or false!

So, even though it doesn't seem like at 1st sight, at the end of those operations expression,
a boolean value will "magically" appear!
And it is thus eligible to be used as a return from a boolean method!

Also, you can use bitwise operators & and | in place of && and ||
when using relational operators! They're even faster!!!

... but I'm just wondering if you chose the three different states to be -1, 0 and 1 for any reason.

They're just arbitrary values; coulda been any other number!

Actually, the most "neatly" way is to create constant variables to act as labels to any arbitrary value:

final static byte stateTitle    = -100;
final static byte statePlaying  = 30;
final static byte stateGameOver = 57;

byte gameState = stateTitle;

...

void draw() {

  ...

  if (gameState == stateTitle)    ...

  if (gameState == stateGameOver) ...

  ...
}