边框圆角练习--跳动的心

　　　　　.all{
            width: 450px;
            height: 400px;
            box-sizing: border-box;
            margin: 200px auto;
            position: relative;
        }
        .left, .right{
            width: 250px;
            height: 250px;
            background: red;
            border-radius: 50%;
            position: absolute;
            top: 0;
            box-shadow: 0 0 40px red;
        }
        .left{
            left: 0;
        }
        .right{  
            right: 0;
        }
        .bottom{
            width: 250px;
            height: 250px;
            background: red;
            position: absolute;
            bottom: 50px;
            left: 50%;
            transform: translateX(-50%) rotateZ(45deg);
            box-shadow: 0 0 40px red;
        }
        .all{
            animation: sport 1s linear 0s infinite normal;
        }
        @keyframes sport {
            0%{
                transform: scale(1);
            }
            50%{
                transform: scale(1.1);
            }
            100%{
                transform: scale(1);
            }
        }