Pumpkin fade C code for ATTiny85

/* pumpkin fade - drives a single RGB LED from an ATTiny85
   Uses 3 channel PWM on digital pins 0,1,4
   John Ridley October 28 2014
   Released into public domain */

#define F_CPU 8000000

#include <avr/io.h>
#include <util/delay.h>

#define RED 0
#define GREEN 1
#define BLUE 2


// stepnum = 0 -> 64
int slider(int from, int to, int stepnum)
{
	int diff = from-to;
	return from - ((diff*stepnum)/64);
}


void main()
{
    /* Port 0,1,4 to output */
    DDRB = 1<<DDB4 | 1<<DDB1 | 1<<DDB0;

    /* both timers to fast PWM mode, no prescaler */
    TCCR0A = 2<<COM0A0 | 2<<COM0B0 | 3<<WGM00;
    TCCR0B = 0<<WGM02 | 1<<CS00;
    TCCR1 = 0<<PWM1A | 0<<COM1A0 | 1<<CS10;
    GTCCR = 1<<PWM1B | 2<<COM1B0;

    /* these are the colors we fade between */
    int colors[8][3] = {
	 {255,0,0},
	 {0,0,255},
	 {255,102,178}, // pink
	 {0,255,0},
	 {255,153,51}, // orange
	 {51,255,255}, // teal
	 {255,0,255}, // magenta
	 {128,255,102}, // yellow
	 };

 	int curcolor = 0;
	int numcolors = 8;

    while (1)
    {
	int nextcolor = curcolor+1;
	if (nextcolor >= numcolors)
		nextcolor = 0;

	for (int fade = 0; fade < 64; fade++)
	{
		int red = slider(colors[curcolor][RED],
		                 colors[nextcolor][RED],
				 fade);
		int green = slider(colors[curcolor][GREEN],
		                 colors[nextcolor][GREEN],
				 fade);
		int blue = slider(colors[curcolor][BLUE],
		                 colors[nextcolor][BLUE],
				 fade);

	        OCR0A = red;
		OCR0B = green;
        	OCR1B = blue;
        	_delay_ms(3);
	}
	curcolor = nextcolor;
    }
}