Tutorial: First Arduino program - Kit's lights

Purpose:
Flash 4 leds from right to left and left to light.

Difficulty / Time to complete:
Beginner / 5 minutes

Tools:

• Arduino board (tested on duemilanove)
• 4 LEDs
• 1 switch
• 1 10K/.25W resistor
• Workstation with Arduino 0.017 or higher
  

Arduino code:

int leds[]={10,11,12,13};   //pins with leds
const int dl = 75;          //delay between moving
const int btn = 9;          //button pin
int btnS = 0;               //button state
int i=0;                    //general purpose counter

void setup(){
for(i=0;ipinMode(leds[i],OUTPUT);
}
pinMode(btn,INPUT);
myflash(leds,sizeof(leds),dl,false);
myflash(leds,sizeof(leds),dl,true);
}

void loop(){
btnS = digitalRead(btn);

if(btnS == HIGH){
myflash(leds,sizeof(leds),dl,false);
myflash(leds,sizeof(leds),dl,true);
delay(250);
}
else{
for(i=0;idigitalWrite(leds[i],LOW);
}
}

//myflash function: flash an array of pins to the R or L
void myflash(int arr[],int size,int delay1,boolean reverse){
int j = 0;
if(reverse==true){
for(j=(size-1);j>=0;j--){
digitalWrite(arr[j],HIGH);
delay(delay1);
digitalWrite(arr[j],LOW);
}
}
else {
for(j=0;jdigitalWrite(arr[j],HIGH);
delay(delay1);
digitalWrite(arr[j],LOW);
}
}
}

Note: After copying-pasting code to the Arduino IDE, press Ctrl+T to fix indents.

The final product (video):