// https://wokwi.com/projects/346217286575587924

# include <Adafruit_NeoPixel.h>

# define TANKSIZE 23    // units and LEDs as well
# define NTANKS 3       // hardware. three tanks

# define LED_PIN    7
# define LED_COUNT 40

Adafruit_NeoPixel rings(LED_COUNT, LED_PIN, NEO_GRB + NEO_KHZ800);

void setup() {
  Serial.begin(115200);
  Serial.println("rings of LEDs\n");

  rings.begin();
  rings.show();
}

int nextLED;

void loop() {
  rings.setPixelColor(nextLED, 0x0); // turn off the one that is on

  nextLED++; // move to next LED

  if (nextLED >= LED_COUNT) // maybe off the end!
    nextLED = 0;

  rings.setPixelColor(nextLED, 0xff0000); // turn on one LED

  rings.show();     // and set all the LEDs to the new values

  delay(133);        // hang out for a bit so we can see it
}