:root {
    --tech-primary: #00f3ff;
    /* 青蓝色 - AI 科技感主色 */
    --tech-primary-rgb: 0, 243, 255;
    --tech-dark: #0a0f1f;
    /* 深蓝黑背景 */
    --tech-card: #161f33;
    /* 卡片深灰蓝 */
    --tech-text: #e0f7ff;
    /* 浅青色文字 */
}

body {
    background: var(--tech-dark);
    color: var(--tech-text);
    font-family: 'Poppins', sans-serif;
    background-image: radial-gradient(circle at 10% 20%, rgba(var(--tech-primary-rgb), 0.1) 0%, transparent 20%),
    radial-gradient(circle at 90% 80%, rgba(var(--tech-primary-rgb), 0.1) 0%, transparent 20%);
    min-height: 100vh;
    margin: 0;
    overflow-x: hidden;
}

/* 玻璃拟态卡片 */

.card {
    background: rgba(22, 31, 51, 0.7) !important;
    /* 半透明背景 */
    backdrop-filter: blur(10px);
    /* 毛玻璃效果 */
    border: 1px solid rgba(var(--tech-primary-rgb), 0.2);
    border-radius: 15px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
    transition: all 0.3s ease;
    color: var(--tech-text);
    overflow: hidden;
    position: relative;
    margin-bottom: 2rem;
}

.card::before {
    content: '';
    position: absolute;
    top: -2px;
    left: -2px;
    right: -2px;
    bottom: -2px;
    background: linear-gradient(45deg, transparent, rgba(var(--tech-primary-rgb), 0.1), transparent);
    border-radius: 18px;
    z-index: -1;
    opacity: 0;
    transition: opacity 0.3s ease;
}

.card:hover {
    transform: translateY(-5px);
    box-shadow: 0 15px 35px rgba(0, 0, 0, 0.4);
}

.card:hover::before {
    opacity: 1;
}

/* 卡片头部发光 */
.card-header {
    background: rgba(0, 216, 255, 0.1) !important;
    border-bottom: 1px solid rgba(var(--tech-primary-rgb), 0.3) !important;
    position: relative;
    overflow: hidden;
}

.card-header::after {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    width: 100%;
    height: 2px;
    background: linear-gradient(90deg, transparent, var(--tech-primary), transparent);
    animation: shine 3s infinite;
}

@keyframes shine {
    0% {
        background-position: -100% 0;
    }
    100% {
        background-position: 100% 0;
    }
}

/* 标题样式 */
h1,
h2,
h3,
h4,
h5 {
    color: #ffffff;
    font-weight: 600;
    text-shadow: 0 0 10px rgba(var(--tech-primary-rgb), 0.5);
}

/* 科技感按钮 */
.btn-tech {
    background: linear-gradient(45deg, var(--tech-primary), #748eff);
    border: none;
    padding: 10px 25px;
    border-radius: 50px;
    font-weight: 500;
    box-shadow: 0 0 15px rgba(var(--tech-primary-rgb), 0.5);
    transition: all 0.3s ease;
}

.btn-tech:hover {
    box-shadow: 0 0 25px rgba(var(--tech-primary-rgb), 0.8);
    transform: scale(1.05);
}

/* 标签样式 */
.badge-tech {
    background: rgba(var(--tech-primary-rgb), 0.2);
    border: 1px solid var(--tech-primary);
    color: var(--tech-primary);
    font-weight: 400;
    padding: 5px 10px;
    border-radius: 8px;
}

/* 代码/终端风格 */
.terminal-box {
    background: #000000 !important;
    border-left: 4px solid var(--tech-primary);
}

/* 脉冲动画点 */
.pulse-dot {
    margin-right: 5px;
    display: inline-block;
    width: 10px;
    height: 10px;
    background-color: var(--tech-primary);
    border-radius: 50%;
    animation: pulse 2s infinite;
}

@keyframes pulse {
    0% {
        box-shadow: 0 0 0 0 rgba(var(--tech-primary-rgb), 0.7);
    }
    70% {
        box-shadow: 0 0 0 10px rgba(var(--tech-primary-rgb), 0);
    }
    100% {
        box-shadow: 0 0 0 0 rgba(var(--tech-primary-rgb), 0);
    }
}

/* 修复：响应式导航栏样式 */
.navbar {
    background: rgba(10, 15, 31, 0.95) !important;
    backdrop-filter: blur(10px);
    border-bottom: 1px solid rgba(var(--tech-primary-rgb), 0.3);
}

/* 修复：移动端折叠菜单样式 */
.navbar-collapse {
    border-radius: 10px;
    margin: 5px 0;
    padding: 10px;
    backdrop-filter: blur(5px);
}

.navbar-nav .nav-link {
    color: var(--tech-text) !important;
    padding: 0.5rem 1rem !important;
    border-radius: 5px;
    transition: all 0.2s;
}

.navbar-nav .nav-link:hover {
    background: rgba(var(--tech-primary-rgb), 0.1);
    color: var(--tech-primary) !important;
}

/* 修复：汉堡图标颜色 */
.navbar-toggler {
    border-color: var(--tech-primary);
}

.navbar-toggler-icon {
    background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 30 30'%3e%3cpath stroke='rgba(0, 243, 255, 0.8)' stroke-linecap='round' stroke-miterlimit='10' stroke-width='2' d='M4 7h22M4 15h22M4 23h22'/%3e%3c/svg%3e");
}

/* ── FOOTER ── */
footer {
    background: var(--tech-dark);
    border-top: 1px solid var(--bs-gray);
    padding: 48px 60px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.footer-logo {
    font-family: 'Space Mono', monospace;
    font-size: 0.9rem;
    color: var(--tech-primary);
}

.footer-copy {
    font-size: 0.78rem;
}

/* 响应式优化 */
@media (max-width: 768px) {
    .card {
        border-radius: 10px;
    }
    h1 {
        font-size: 1.8rem;
    }

    /* 修复：移动端菜单堆叠 */
    .navbar-nav {
        flex-direction: column;
        gap: 0.5rem;
    }

    footer {
        flex-direction: column;
        gap: 16px;
        text-align: center;
    }
}

#courseTabs {
    justify-content: space-around;
}