File content as of revision 1:486592635dfd:

#include "mbed.h"

DigitalIn sw(p5);
DigitalOut myled1(LED1);
DigitalOut myled2(LED2);
DigitalOut myled3(LED3);
DigitalOut myled4(LED4);
DigitalOut leds[] = {myled1, myled2, myled3, myled4};

int timeBase = 0;
int ledPx = 0;

void tick() {
    if ((timeBase += 1) == 10) {
        timeBase = 0;
    }
}

void countupLed() {
    if (sw == 0) {
        ledPx++;
        if (ledPx == 4) {
            ledPx = 0;
        }
    } else {
        ledPx--;
        if (ledPx == -1) {
            ledPx = 4;
        }
    }
}

void blink(DigitalOut *led, int timing) {
    if ((timeBase % timing) == 0) {
        if (led->read() == 0) {
            led->write(1);
        } else {
            led->write(0);
        }
    }
}

int main() {
    while(1) {
        blink(&leds[ledPx], 1);
        countupLed();
        tick();
        wait(0.1);
    }
}