function euclid2d(x1, y1, x2, y2) {
    return Math.sqrt(
        Math.pow(x1-x2, 2) +
        Math.pow(y1-y2, 2)
    );
}

function norm2d(x, y) {
    return Math.sqrt(x*x + y*y);
}

function deg2rad(angle) {
    return angle*(Math.PI/180.0);
}

function rad2deg(angle) {
    return angle*(180.0/Math.PI);
}

function paddingString(s, mask) {
    size = mask.length;

    return (mask + s).slice(-size);
}

function addClass(element, cls) {
    element.className = element.className + " " + cls;
}

function removeClass(element, cls) {
    element.className = "";
}

function linear(a, b, t) {
    return creatine.clip(a + t*(b-a), a, b);
}

function ilinear(a, b, t) {
    // return a - t*(a-b);
    return creatine.clip(a - t*(a-b), b, a);
}

// function