heißer Draht mit LCD Display Fehler und Zeit Messung

// software for http://www.kreativekiste.de/elektro/dem-heissen-draht-auf-der-spur
// developed by Timo Denk (Nov 2014)
//
// wiring:
// 0: start
// 1: stop
// 2: mistake
// 3: buzzer
// A0: penalty time
// A4: display SDA
// A5: display SCL

// libraries
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x3F,20,4);

const byte startPin = 0, stopPin = 1, mistakePin = 2, buzzerPin = 3, penaltyTimePin = A0;
const byte minPenaltyTime = 1, maxPenaltyTime = 17; // [t] = 1 s

const String penaltyTimeString = "Fehler", finalTimeString = "Endzeit", timeString = "Zeit", commercialString = "www.kreativekiste.de", mistakeString = "Berührt!!!", totalTime = "Gesamtzeit";

long millisStart, millisEnd;

int mistakes, penaltyTime, lastPenaltyTime;

void setup() {
lcd.init();
lcd.backlight();

pinMode(startPin, INPUT);
pinMode(stopPin, INPUT);
pinMode(mistakePin, INPUT);
pinMode(buzzerPin, OUTPUT);
digitalWrite(buzzerPin, LOW);
digitalWrite(startPin, HIGH);
digitalWrite(stopPin, HIGH);
digitalWrite(mistakePin, HIGH);
}

void loop() {
clearScreen();
printStringCenter(1, "Heisser Draht");

printStringCenter(2, "Strafzeit einstellen");
lastPenaltyTime = 0, penaltyTime = 0;
// waiting for game to start
while (digitalRead(startPin) == HIGH) {
penaltyTime = (byte)round(map(analogRead(penaltyTimePin), 0, 1023, minPenaltyTime, maxPenaltyTime));
if (penaltyTime != lastPenaltyTime) {
clearRow(3);
printStringCenter(3, String(penaltyTime) + " s");
lastPenaltyTime = penaltyTime;
}
}

// game running
millisStart = millis();
clearScreen();
mistakes = 0;
while (digitalRead(stopPin) == HIGH) {
// check for mistakes
printStatusOnScreen();
if (digitalRead(mistakePin) == LOW) {
mistakes++;
digitalWrite(buzzerPin, HIGH);
printStatusOnScreen();
delay(500);
digitalWrite(buzzerPin, LOW);
}
delay(10);
}

// game finished
millisEnd = millis();
clearScreen();
clearRow(0);
printStringCenter(0, "Spiel beendet!");
printStatusOnScreen();
delay(10000);
}

void printStatusOnScreen() {
int playingTime = round((millis() - millisStart)/1000), penaltyTimeSum = mistakes * penaltyTime;
printStringCenter(1, "Spielzeit: " + sec2MinSecString(playingTime));
printStringCenter(2, "Fehler: " + String(mistakes) + " x " + String(penaltyTime) + "s");
printStringCenter(3, "Gesamt: " + sec2MinSecString(playingTime + penaltyTimeSum));
}

void showCommercial() {
clearRow(0);
printStringCenter(0, commercialString);
}

void clearScreen() {
for (byte i = 0; i < 4; i++)
clearRow(i);

showCommercial();
}

void printStringCenter(byte row, String string) {
lcd.setCursor((int)((20 - string.length()) / 2), row);
lcd.print(string);
}

void clearRow(byte row) {
lcd.setCursor(0, row);
lcd.print(" ");
}

String sec2MinSecString(int input) { // converts seconds to a string like "minutes:seconds"
String minutes = String((int)(input / 60));
String seconds = String(input % 60);
if (seconds.length() == 1)
seconds = "0" + seconds;
//if (minutes.length() == 1)
// minutes = "0" + minutes;
return minutes + ":" + seconds + " ";
}