body {
    height: 100vh;
    background: #e7e7e7 url("../images/bg.jpg") center no-repeat fixed;
    background-size: cover;
    display: flex;
    justify-content: center;
    align-items: center;
}

/* 主体 div 样式 */
.container {
    background-color: #e7e7e7;
    border-radius: 0.7rem;
    box-shadow: 0 0.9rem 1.7rem rgba(0, 0, 0, 0.25),
        0 0.7rem 0.7rem rgba(0, 0, 0, 0.22);
    height: 420px;
    max-width: 750px;
    overflow: hidden;
    position: relative;
    width: 100%;
}



.container-form {
    height: 100%;
    position: absolute;
    top: 0;
    transition: all 0.6s ease-in-out;
}

.container-signin {
    left: 0;
    width: 50%;
    z-index: 2;
}

.container-signup {
    left: 0;
    opacity: 0;
    width: 50%;
    z-index: 1;
}

.form {
    background-color: #e7e7e7;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-direction: column;
    padding: 0 3rem;
    height: 100%;
    text-align: center;
}

.form-title {
    font-weight: 300;
    margin: 0;
    margin-bottom: 1.25rem;
}


.link {
    color: #333;
    font-size: 0.9rem;
    margin: 1.5rem 0;
    text-decoration: none;
}

.input {
    width: 100%;
    background-color: #fff;
    padding: 0.9rem 0.9rem;
    margin: 0.5rem 0;
    border: none;
    outline: none;
}


.btn {
    background-color: #f25d8e;
    box-shadow: 0 4px 4px rgba(255, 112, 159, .3);
    border-radius: 5px;
    color: #e7e7e7;
    border: none;
    cursor: pointer;
    font-size: 0.8rem;
    font-weight: bold;
    letter-spacing: 0.1rem;
    padding: 0.9rem 4rem;
    text-transform: uppercase;
    transition: transform 80ms ease-in;
}

.form>.btn {
    margin-top: 1.5rem;
}

.btn:active {
    transform: scale(0.95);
}

.container-overlay {
    height: 100%;
    left: 50%;
    overflow: hidden;
    position: absolute;
    top: 0;
    transition: transform 0.6s ease-in-out;
    width: 50%;
    z-index: 100;
}

.overlay {
    width: 200%;
    height: 100%;
    position: relative;
    left: -100%;
    background: url("../images/bg.jpg") no-repeat center fixed;
    background-size: cover;
    transition: transform 0.6s ease-in-out;
    transform: translateX(0);
}

.overlay-panel {
    height: 100%;
    width: 50%;
    position: absolute;
    top: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    flex-direction: column;
    transform: translateX(0);
    transition: transform 0.6s ease-in-out;
}

.overlay-left {
    transform: translateX(-20%);
}

.overlay-right {
    right: 0;
    transform: translateX(0);
}

.panel-active .overlay-left {
    transform: translateX(0);
}

.panel-active .container-overlay {
    transform: translateX(-100%);
}

.panel-active .overlay {
    transform: translateX(50%);
}

.panel-active .container-signin {
    transform: translateX(100%);
}

.panel-active .container-signup {
    opacity: 1;
    z-index: 5;
    transform: translateX(100%);
}