Revision control
++ <svg xmlns="http://www.w3.org/2000/svg" width="100" height="100">
++ <style>
++ @keyframes opacity {
++ 0% {fill-opacity: 0; stroke-opacity: 0;}
++ 100% {fill-opacity: 1; stroke-opacity: 1;}
++ }
++ rect {
++ animation-duration: 1s;
++ animation-name: opacity;
++ animation-iteration-count: 1;
++ }
++ </style>
++ <rect width="100" height="100" fill="green" stroke="black" stroke-width="6"/>
++ </svg>