// use the FastLED library (someone's pre-written code)
#include <FastLED.h>

// set how many LEDs there are and the data pin.
const int numLeds = 30;
const int ledStripPin = 6;

// this creates an array to reference our LEDs
CRGB leds[numLeds];

void setup() {
  // tells the FastLED code e.g. what LEDs we are using, the data pin
  FastLED.addLeds<NEOPIXEL, ledStripPin>(leds, numLeds);

  // limit the strip's draw to 400mA at 5v
  FastLED.setMaxPowerInVoltsAndMilliamps(5, 400);

  // turns the brightness down (so my eyes don't hurt)
  FastLED.setBrightness(8);
}

void loop() {

for (int light = 0; light < 10; light++) {
  leds[light] = CRGB::Red;
  leds[10+light] = CRGB::Blue;
  leds[20+light] = CRGB::Green;

  FastLED.show();
  delay(500);
}

}