final static byte stateLogo    = 1;
final static byte stateLoading = 2;
final static byte stateRunning = 3;
// and so on...
byte state = stateLogo;

// ...

void setup() {
  // ...
}

void draw() {
  // ...
  if (state == stateLogo) {
    // call some displayLogo function
    state = stateLoading;
  }

  else if (state == stateLoading) {
    // call loading function
    state = stateRunning;
  }

  else if (state == stateRunning) {
    // your normal running code
    // ...
  }
}