Simple elevator

#define USE_OCTOWS2811
#include<OctoWS2811.h>
#include <FastLED.h>

#define NUM_STRIPS 8
#define NUM_LEDS_PER_STRIP    64
#define NUM_LEDS 512
#define MAX_BRIGHTNESS 128

CRGB leds[NUM_LEDS];

#define elevator_size 4   // these are not changing during program execution
#define top_floor 10      // but you can modify them each time you recompile
#define floor_height 8    // to change the basic behaviour of your sketch

int current_floor = 0;   // these will be modified actively during program execution
int which_floor = 0;
int elevator_position = 0;

void setup() {

  Serial.begin(9600);

  LEDS.addLeds<OCTOWS2811, RGB>(leds, NUM_LEDS_PER_STRIP);
  FastLED.setBrightness(MAX_BRIGHTNESS);
  fill_solid(leds, NUM_LEDS, CRGB::Black);
  for (int i = 0; i < elevator_size; i++){
      leds[i] = CRGB::Red;
    }
  FastLED.show();
  delay(2000);

}
void loop(){

which_floor = random8(0, top_floor);

Serial.print("current_floor = ");
Serial.print(current_floor);
Serial.print(",  which_floor = ");
Serial.println(which_floor);

if (which_floor > current_floor) {    // Going up
  for ( elevator_position = current_floor*floor_height;
        elevator_position <= which_floor*floor_height;
        elevator_position++) {

    Serial.print("elevator_position = ");
    Serial.println(elevator_position);

    fill_solid(leds, NUM_LEDS, CRGB::Black);
    for (int i = 0; i < elevator_size; i++) leds[elevator_position+i] = CRGB::Red;
    FastLED.show();
    delay(200);
  }
}

else {      // Going down or just staying there
  for ( elevator_position = current_floor*floor_height;
        elevator_position >= which_floor*floor_height;
        elevator_position--) {

    Serial.print("elevator_position = ");
    Serial.println(elevator_position);

    fill_solid(leds, NUM_LEDS, CRGB::Black);
    for (int i = 0; i < elevator_size; i++) leds[elevator_position+i] = CRGB::Red;
    FastLED.show();
    delay(200);
  }
}

current_floor = which_floor;

delay(2000);                 // or any value you want or replace 2000 with some random value !?

}