#include "FastLED.h"

FASTLED_USING_NAMESPACE

#if defined(FASTLED_VERSION) && (FASTLED_VERSION < 3001000)
#warning "Requires FastLED 3.1 or later; check github for latest code."
#endif

#define DATA_PIN    10
//#define CLK_PIN   4
#define LED_TYPE    WS2811
#define COLOR_ORDER GRB
#define NUM_LEDS    20
CRGB leds[NUM_LEDS];

#define BRIGHTNESS          96
#define DURATION 2.0


unsigned long start = 0;

void setup() {
  // put your setup code here, to run once:


  // tell FastLED about the LED strip configuration
  FastLED.addLeds<LED_TYPE, DATA_PIN, COLOR_ORDER>(leds, NUM_LEDS).setCorrection(TypicalLEDStrip);
  //FastLED.addLeds<LED_TYPE,DATA_PIN,CLK_PIN,COLOR_ORDER>(leds, NUM_LEDS).setCorrection(TypicalLEDStrip);

  // set master brightness control
  FastLED.setBrightness(BRIGHTNESS);

  start = millis();
}

void loop() {
  // put your main code here, to run repeatedly:

  float t = millis() - start;


  if (t <= 10000) {
    float seconds = t/1000.0;

    int st = NUM_LEDS / DURATION * (seconds);
    for (int i = 0; i < st; i++) {
      leds[i] = CRGB(255, 0, 0);
    }
  }
  else {
    for (int i = 0; i < NUM_LEDS; i++) {
      leds[i] = CRGB(255, 0, 0);
    }
  }

  FastLED.show();

}