File content as of revision 0:f0739e8427ec:

#include "mbed.h"

PwmOut led1(LED1),led2(LED2),led3(LED3),led4(LED4);
float a=0.25f,b=0,c=-0.25f,d=-0.5f;
int aa=0,bb=0,cc=0,dd=0;

int main() {
    while (1) {
        if (a>=1) {
            aa=1;
        } else if (a<-0.5) {
            aa=0;
        };
        if (b>=1) {
            bb=1;
        } else if (b<-0.5) {
            bb=0;
        };
        if (c>=1) {
            cc=1;
        } else if (c<-0.5) {
            cc=0;
        };
        if (d>=1) {
            dd=1;
        } else if (d<-0.5) {
            dd=0;
        };

        if (aa==0) {
            a+=0.025f;
        } else {
            a-=0.075f;
        };
        if (bb==0) {
            b+=0.025f;
        } else {
            b-=0.075f;
        };
        if (cc==0) {
            c+=0.025f;
        } else {
            c-=0.075f;
        };
        if (dd==0) {
            d+=0.025f;
        } else {
            d-=0.075f;
        };

        led1 = a;
        led2 = b;
        led3 = c;
        led4 = d;

        wait(0.025);
    }
}