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

#define PWM_PIN PB1
#define SWITCH_PIN PD2

int main(void) {
    DDRB |= (1 << PWM_PIN);  // Configure PWM pin as output
    DDRD &= ~(1 << SWITCH_PIN);  // Configure switch pin as input
    PORTD |= (1 << SWITCH_PIN);  // Enable internal pull-up resistor

    // Configure Timer1 for PWM operation
    TCCR1A |= (1 << COM1A1) | (1 << WGM11);
    TCCR1B |= (1 << WGM13) | (1 << WGM12) | (1 << CS11);
    ICR1 = 625;

    uint8_t duty_cycle = 0;

    while (1) {
        // Read switch state
        if (!(PIND & (1 << SWITCH_PIN))) {
            // Switch is pressed, increase duty cycle
            duty_cycle += 10;
            if (duty_cycle > 100) {
                duty_cycle = 100;
            }
        } else {
            // Switch is not pressed, decrease duty cycle
            duty_cycle -= 10;
            if (duty_cycle < 0) {
                duty_cycle = 0;
            }
        }

        // Set duty cycle
        OCR1A = duty_cycle * 6.25;

        // Delay to allow the human eye to perceive the change
        _delay_ms(50);
    }
}