#include <Adafruit_NeoPixel.h>

// --- Configuration ---
#define LED_PIN        2    // The Arduino pin connected to the NeoPixel strip's Data In
#define LED_COUNT      60   // Number of LEDs on your strip
#define BRIGHTNESS     200  // Set brightness (0-255). Be mindful of power consumption.

// Create an instance of the Adafruit_NeoPixel class
Adafruit_NeoPixel strip(LED_COUNT, LED_PIN, NEO_GRB + NEO_KHZ800);

void setup() {
  // Initialize the NeoPixel strip
  strip.begin();
  strip.setBrightness(BRIGHTNESS);
  strip.show(); // Initialize all pixels to 'off'
}

void loop() {
  // Continuously run the bouncing balls effect
  bouncingBalls();
}

/**
 * @brief Bouncing Balls Effect
 * Simulates two "balls" of light that are randomly "kicked" upwards from the
 * bottom of the strip. They then fall back down with simulated gravity.
 * A fading trail is left behind each ball.
 */
void bouncingBalls() {
  // Static variables are crucial here. They preserve their values between
  // each call to the loop(), allowing the balls to remember their position and velocity.
  static float pos1 = 0, vel1 = 0; // Position and velocity for ball 1
  static float pos2 = 0, vel2 = 0; // Position and velocity for ball 2

  // This constant determines how strongly the balls are pulled "down" (towards pixel 0).
  // A larger value means they fall faster.
  const float gravity = -0.4;

  // --- Step 1: Fade all existing pixels ---
  // This creates the "trails" behind the moving balls.
  // The 0.85 multiplier means each pixel loses 15% of its brightness each frame.
  for(int i = 0; i < strip.numPixels(); i++) {
    uint32_t color = strip.getPixelColor(i);
    uint8_t r = (uint8_t)( (color >> 16) * 0.85 );
    uint8_t g = (uint8_t)( ((color >> 8) & 0xFF) * 0.85 );
    uint8_t b = (uint8_t)( (color & 0xFF) * 0.85 );
    strip.setPixelColor(i, strip.Color(r, g, b));
  }

  // --- Step 2: Update physics for Ball 1 ---
  vel1 = vel1 + gravity; // Apply gravity to velocity
  pos1 = pos1 + vel1;    // Apply velocity to position

  // Check if the ball has hit the "floor" (or gone below it)
  if (pos1 < 0) {
    pos1 = 0; // Reset position to the floor
    // Give the ball a random chance to be "kicked" back up
    if (random(100) < 40) { // 40% chance of a new kick
      // Give it a new random upward velocity
      vel1 = random(60, 95) / 10.0; // Random value between 6.0 and 9.5
    }
  }

  // --- Step 3: Update physics for Ball 2 ---
  // This ball is updated independently with different random chances
  vel2 = vel2 + gravity;
  pos2 = pos2 + vel2;

  if (pos2 < 0) {
    pos2 = 0;
    // This ball has a different chance and velocity range for variety
    if (random(100) < 25) { // 25% chance of a new kick
      vel2 = random(50, 80) / 10.0; // Random value between 5.0 and 8.0
    }
  }
  
  // --- Step 4: Draw the balls at their new positions ---
  // Use constrain to make sure the position is a valid pixel index
  int intPos1 = constrain((int)pos1, 0, LED_COUNT - 1);
  int intPos2 = constrain((int)pos2, 0, LED_COUNT - 1);

  // Draw the two balls with distinct, bright colors
  strip.setPixelColor(intPos1, strip.Color(255, 0, 100)); // Hot Pink
  strip.setPixelColor(intPos2, strip.Color(0, 100, 255)); // Bright Blue

  // --- Step 5: Update the physical LED strip ---
  strip.show();
  
  // A short delay to control the animation speed.
  // Smaller delay = faster animation.
  delay(20);
}