Code

#define DELAY            50
#define PLAY_CODE         1
#define RECEIVE_CODE      2
#define VICTORY           3
#define DEFEAT            4

const int detectPinArr[]={3,5,7,9},
    lightPinArr[]={2,4,6,8},
    buzzerPin=10,
    toneArr[]={523.25,659.25,783.99,987.77};
int pinAmount=4;
int gameState=PLAY_CODE;
int codeLength=4;
int colorCode[10];
int currCodeIndex = 0;

void codeRandomize() {
  for(int i=0;i<codeLength;i++) {
    colorCode[i]=random(1,5);
  }
}

void setup()
{
  for(int i=0;i<pinAmount;i++) {
    pinMode(detectPinArr[i],INPUT);
    digitalWrite(detectPinArr[i],HIGH);
    pinMode(lightPinArr[i],OUTPUT);
  }
  pinMode(buzzerPin,OUTPUT);
  randomSeed(analogRead(0));
}

void loop()
{
  switch(gameState) {
    case PLAY_CODE:
      codeRandomize();
      for(int i=0;i<codeLength;i++) {
        digitalWrite(lightPinArr[colorCode[i]-1],HIGH);
        tone(buzzerPin,toneArr[colorCode[i]-1]);
        delay(1000);
        digitalWrite(lightPinArr[colorCode[i]-1],LOW);
        noTone(buzzerPin);
        delay(100);
      }
      currCodeIndex=0;
      gameState=RECEIVE_CODE;
      break;
    case RECEIVE_CODE:
      for(int i=0;i<pinAmount;i++) {
        if(!digitalRead(detectPinArr[i])) {
          if(colorCode[currCodeIndex]-1==i) {
            if(currCodeIndex<codeLength-1) {
              currCodeIndex++;
            } else {
              gameState=VICTORY;
              currCodeIndex=0;
            }
          } else {
            gameState=DEFEAT;
          }
          digitalWrite(lightPinArr[i],HIGH);
          tone(buzzerPin,toneArr[i]);
          delay(600);
          digitalWrite(lightPinArr[i],LOW);
          noTone(buzzerPin);
          delay(100);
        }
      }
      break;
    case VICTORY:
      digitalWrite(lightPinArr[0],HIGH);
      digitalWrite(lightPinArr[1],HIGH);
      digitalWrite(lightPinArr[2],HIGH);
      digitalWrite(lightPinArr[3],HIGH);
      tone(buzzerPin,523.25);
      delay(500);
      digitalWrite(lightPinArr[0],LOW);
      digitalWrite(lightPinArr[1],LOW);
      digitalWrite(lightPinArr[2],LOW);
      digitalWrite(lightPinArr[3],LOW);
      noTone(buzzerPin);
      delay(500);
      digitalWrite(lightPinArr[0],HIGH);
      digitalWrite(lightPinArr[1],HIGH);
      digitalWrite(lightPinArr[2],HIGH);
      digitalWrite(lightPinArr[3],HIGH);
      tone(buzzerPin,659.25);
      delay(500);
      digitalWrite(lightPinArr[0],LOW);
      digitalWrite(lightPinArr[1],LOW);
      digitalWrite(lightPinArr[2],LOW);
      digitalWrite(lightPinArr[3],LOW);
      noTone(buzzerPin);
      delay(500);
      digitalWrite(lightPinArr[0],HIGH);
      digitalWrite(lightPinArr[1],HIGH);
      digitalWrite(lightPinArr[2],HIGH);
      digitalWrite(lightPinArr[3],HIGH);
      tone(buzzerPin,783.99);
      delay(450);
      noTone(buzzerPin);
      delay(100);
      tone(buzzerPin,783.99);
      delay(450);
      digitalWrite(lightPinArr[0],LOW);
      digitalWrite(lightPinArr[1],LOW);
      digitalWrite(lightPinArr[2],LOW);
      digitalWrite(lightPinArr[3],LOW);
      noTone(buzzerPin);
      delay(500);
      gameState=PLAY_CODE;
      break;
    case DEFEAT:
      digitalWrite(lightPinArr[3],HIGH);
      tone(buzzerPin,622.25);
      delay(500);
      digitalWrite(lightPinArr[3],LOW);
      noTone(buzzerPin);
      delay(500);
      digitalWrite(lightPinArr[3],HIGH);
      tone(buzzerPin,523.25);
      delay(500);
      digitalWrite(lightPinArr[3],LOW);
      noTone(buzzerPin);
      delay(500);
      digitalWrite(lightPinArr[3],HIGH);
      tone(buzzerPin,392.00);
      delay(1000);
      digitalWrite(lightPinArr[3],LOW);
      noTone(buzzerPin);
      delay(500);
      gameState=PLAY_CODE;
      break;
    default:
      break;
  }
  delay(DELAY);
}