.balloon {
    --balloonDimension: 15vmax; /* 15% of min(viewport width, height) */
    width: var(--balloonDimension);
    height: var(--balloonDimension);
    border-radius: 100% 100% 15% 100%;
    margin: 0 0 0 25px;
    transform: rotateZ(45deg);
    position: fixed;
    bottom: calc(-1 * var(--balloonDimension));
    left: 0;
    background-color: aqua;
}
.balloon::before {
    content: "";
    width: 10%;
    height: 25%;
    background: radial-gradient(circle, rgba(255,255,255,.7) 0%, rgba(255,255,255,.1) 100%);
    position: absolute;
    left: 15%;
    top: 45%;
    border-radius: 100%;
}
.balloon::after {
    content: "";
    width: 13%;
    height: 5%;
    background-color: inherit;
    position: absolute;
    left: 90%;
    top: 94%;
    border-radius: 22%;
    transform: rotateZ(-45deg);
}
.balloon .string {
    position: absolute;
    background-color: #990;
    width: 2px;
    height: calc(var(--balloonDimension) * .6);
    transform-origin: top center;
    transform: rotateZ(-45deg);
    top: calc(var(--balloonDimension) - 6px);
    left: calc(var(--balloonDimension) - 8px);
}
.yellow{
    background-color: rgba(150, 150, 0, .45);
}
.green{
    background-color: rgba(0, 150, 0, .45);
}
.blue{
    background-color: rgba(0, 0, 150, .45);
}
.red{
    background-color: rgba(150, 0, 0, .45);
}