GlowBeast arduino code - breathing glow effect

GlowBeast.pde

// Just for reference
//int static_pin = 11;
//int dynamic_pins[] = {3, 5, 6, 9, 10};

// I'm using parallel arrays to hold my object info here - each column is
// an LED.

// CONSTANTS
int pwm_pins[]      = {   3,   5,   6,   9,  10,  11 };
float base_speeds[] = {   1,   1,   1,   1,   1,  .5 }; // in deg/cycle
float speeds[]      = {   1,   1,   1,   1,   1,  .5 }; // in deg/cycle, should be a copy of base_speeds[]
int max_bright[]    = { 255, 255, 255, 255, 255, 128 };
int min_bright[]    = { 100, 100, 100, 100, 100,  64 };

// DYNAMIC STATE
// Different states:
//   0 = rising
//   1 = falling
int state[]         = {   0,   0,   0,   0,   0,   0 };

// Current "degrees" in a cycle (0-360);
float value[]       = {   0,   0,   0,   0,   0,   0 };

// Current value, in # of cycles, to pause before resuming animation
int pause[]         = {   0, 100, 200, 300, 400,   0 };
 
int superbright_dim = 64;

// The time, in ms, between each step
int time_step = 20; 

// The factor of the base_speed that the speed will be modified each round
float speed_mod_factor = .5;
 
void setup()
{ 
  for ( int i = 0; i < 6; i++) {
      analogWrite(pwm_pins[i], min_bright[i]);
  }
} 
 
void loop() 
{ 
  for ( int i = 0; i < 6; i++ ) {
    if ( pause[i] > 0 ) {
      pause[i]--;
    } else {
      value[i] += speeds[i];
    
      if ( value[i] > 90 && state[i] == 0 ) {
        value[i] = 90;
        state[i] = 1; // falling
      } else if ( value[i] > 180 ) {
        float speed_mod = base_speeds[i] * speed_mod_factor;
        
        // It can get slower, but not faster.
        int low = int((base_speeds[i] - speed_mod) * 1000);
        int high = int(base_speeds[i] * 1000);
        speeds[i] = float(random(low, high)) / 1000.0; // random returns long
        
        value[i] -= 180;
        state[i] = 0; // rising
      }
      
      analogWrite(pwm_pins[i], sin_inverted(value[i], i));
    }
  }

  delay(time_step);
} 

int sin_inverted(float input, int led) {
  input = input + 90;
 
  if ( input > 360 ) {
    input -= 360;
  }
  
  float rads = radians(input);
  float output = 1 - abs(sin(rads));
  
  return convert_output(output, led);
}

// Converts something from 0 to 1 into brightnesses
int convert_output(float output, int led) {
  return floor(output * (max_bright[led] - min_bright[led])) + min_bright[led];
}