* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

.video-background {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    overflow: hidden;
}

.video-background video {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

body {
    font-family: 'Microsoft YaHei', sans-serif;
    line-height: 1.6;
    background: transparent;
}

.container {
    max-width: 800px;
    margin: 1rem auto;
    padding: 0 2rem;
    padding-left: 220px;
}

.profile-section {
    background: rgba(25, 25, 35, 0.2);
    backdrop-filter: blur(8px);
    padding: 2.5rem;
    border-radius: 20px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
    text-align: center;
    border: 1px solid rgba(255, 255, 255, 0.1);
}

.profile-image {
    width: 200px;
    height: 200px;
    border-radius: 20px;
    object-fit: cover;
    margin-bottom: 1rem;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    margin-left: auto;
    margin-right: auto;
}

.profile-video {
    width: 100%;
    max-width: 600px;
    border-radius: 20px;
    margin: 2rem auto;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
}

.profile-header h1 {
    font-size: 2rem;
    margin: 1rem 0;
    color: white;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

.intro-text {
    max-width: 600px;
    margin: 0 auto;
    color: rgba(255, 255, 255, 0.9);
    font-size: 1.1rem;
}

.intro-text p {
    margin-bottom: 1rem;
}

.navbar {
    width: 200px;
    background-color: rgba(20, 20, 20, 0.8);
    position: fixed;
    height: 100vh;
    left: 0;
    top: 0;
    overflow-y: auto;
    box-shadow: 5px 0 15px rgba(0, 0, 0, 0.4);
    text-align: center;
}

.nav-brand {
    color: #f0f0f0;
    padding: 20px;
    font-size: 1.5em;
    text-align: center;
    background-color: rgba(0, 0, 0, 0.9);
}

.nav-item {
    color: #f0f0f0;
    text-decoration: none;
    padding: 12px 15px;
    display: block;
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
}

.nav-item-container:hover .nav-item {
    background-color: rgba(255, 255, 255, 0.1);
}

.sub-nav {
    display: none;
    background-color: rgba(20, 20, 20, 0.8);
    transition: all 0.3s ease;
    opacity: 0;
    transform: translateX(-10px);
}

.nav-item-container:hover .sub-nav {
    display: block;
    opacity: 1;
    transform: translateX(0);
    animation: slideDown 0.35s ease-out;
}

@keyframes slideDown {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.sub-nav-item {
    color: #ccc;
    text-decoration: none;
    padding: 8px 20px;
    display: block;
    transition: background-color 0.3s ease, color 0.3s ease;
    position: relative;
    z-index: 1;
}

a:hover {
    text-decoration: none;
}

.sub-nav-item:hover {
    background-color: rgba(255, 255, 255, 0.1);
    color: #fff;
}

.back-to-home {
    position: fixed;
    top: 20px;
    right: 20px;
    z-index: 1000;
}

.back-to-home a {
    display: inline-block;
    padding: 10px 20px;
    background: rgba(25, 25, 35, 0.3);
    backdrop-filter: blur(8px);
    color: rgba(255, 255, 255, 0.9);
    text-decoration: none;
    border-radius: 5px;
    transition: all 0.3s ease;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.2);
}

.back-to-home a:hover {
    background: rgba(45, 45, 55, 0.4);
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.3);
}

@media screen and (max-width: 1200px) {
    .container {
        padding-left: 0;
        max-width: 95%;
        margin-top: 2rem;
    }
    
    .navbar {
        width: 180px;
    }
    
    .profile-image {
        width: 180px;
        height: 180px;
    }
}

@media screen and (max-width: 992px) {
    .navbar {
        width: 160px;
    }
    
    .container {
        padding: 0 1.5rem;
    }
    
    .nav-brand {
        padding: 15px;
        font-size: 1.3em;
    }
    
    .nav-item {
        padding: 10px;
    }
    
    .profile-section {
        padding: 2rem;
    }
    
    .profile-header h1 {
        font-size: 1.8rem;
    }
    
    .intro-text {
        font-size: 1rem;
    }
}

@media screen and (max-width: 768px) {
    .navbar {
        width: 100%;
        height: auto;
        position: relative;
        box-shadow: none;
        padding: 0.5rem 0;
    }
    
    .nav-links {
        display: flex;
        flex-wrap: wrap;
        justify-content: center;
    }
    
    .nav-item-container {
        margin: 0 5px;
        position: relative;
    }
    
    .nav-brand {
        padding: 10px;
        font-size: 1.2em;
    }
    
    .container {
        padding: 0 1rem;
        margin-top: 1rem;
    }
    
    .nav-item-container:hover .sub-nav {
        position: absolute;
        left: 0;
        width: 200px;
        animation: none;
        background-color: rgba(30, 30, 30, 0.9);
        z-index: 100;
    }
    
    .sub-nav-grid {
        display: grid;
        grid-template-columns: repeat(2, 1fr);
        gap: 5px;
        padding: 0.5rem;
    }
    
    .sub-nav-item {
        padding: 10px 15px;
        text-align: center;
    }
    
    .profile-image {
        width: 150px;
        height: 150px;
    }
    
    .profile-section {
        padding: 1.5rem;
    }
    
    .back-to-home {
        top: auto;
        bottom: 20px;
        right: 20px;
    }
}

@media screen and (max-width: 576px) {
    .nav-links {
        flex-direction: column;
        align-items: center;
    }
    
    .nav-item-container {
        width: 100%;
        margin: 0;
    }
    
    .nav-item {
        width: 100%;
        text-align: center;
    }
    
    .nav-item-container:hover .sub-nav {
        position: static;
        width: 100%;
    }
    
    .sub-nav-grid {
        display: grid;
        grid-template-columns: repeat(2, 1fr);
    }
    
    .profile-image {
        width: 120px;
        height: 120px;
    }
    
    .profile-header h1 {
        font-size: 1.6rem;
    }
    
    .profile-section {
        padding: 1rem;
    }
    
    .intro-text {
        font-size: 0.9rem;
    }
    
    .back-to-home a {
        padding: 8px 15px;
        font-size: 0.9em;
    }
}

.content-container {
    margin-left: 200px;
    padding: 0;
    width: calc(100% - 200px);
    height: 100vh;
    background: transparent;
    position: fixed;
    top: 0;
    right: 0;
}

.content-section {
    background: transparent;
    padding: 20px;
    border-radius: 10px;
    color: white;
    margin-top: 20px;
}

.content-frame {
    width: 100%;
    height: 100%;
    border: none;
    background: transparent !important;
}

/* 第09次作业（美的）的特殊样式 */
.content-frame[src*="第09次作业/midea.html"] {
    background: white;
}

@media screen and (max-width: 768px) {
    .content-container {
        margin-left: 0;
        width: 100%;
        padding: 0;
    }
}

.default-content {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100%;
    text-align: center;
}

.default-content h1 {
    font-size: 2.5rem;
    color: white;
    text-shadow: 3px 3px 6px rgba(0, 0, 0, 0.2),
                 0 0 10px rgba(0, 0, 0, 0.1);
    font-weight: bold;
}