/* --- 全局与变量定义 --- */
:root {
    --primary-color: #007bff; /* 主题蓝色 */
    --primary-hover-color: #0056b3;
    --secondary-color: #f8f9fa; /* 浅灰白色 */
    --text-color: #333;
    --light-text-color: #ffffff;
    --border-radius: 12px;
    --box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
    --transition-speed: 0.3s;
}

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

body {
    font-family: 'Helvetica Neue', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
    background-color: #e9ecef;
    color: var(--text-color);
    line-height: 1.6;
}

/* --- 主容器与背景 --- */
.dashboard-container {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    /* 【重要】请将此URL替换为您自己的背景图片 */
    background-image: url('https://images.unsplash.com/photo-1518709268805-4e9042af2176?q=80&w=2670&auto=format&fit=crop');
    background-size: cover;
    background-position: center;
    background-attachment: fixed;
    position: relative;
}

.dashboard-container::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.4); /* 半透明黑色遮罩，增强文字可读性 */
    z-index: 1;
}

/* --- 头部 --- */
.dashboard-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 15px 30px;
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px); /* 毛玻璃效果 */
    border-bottom: 1px solid rgba(255, 255, 255, 0.2);
    position: relative;
    z-index: 2;
}

.logo {
    display: flex;
    align-items: center;
    color: var(--light-text-color);
    font-size: 1.8rem;
    font-weight: bold;
    text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.5);
}

.logo img {
    height: 40px;
    margin-right: 10px;
}

.user-controls {
    display: flex;
    align-items: center;
    gap: 15px;
}

.welcome-text {
    color: var(--light-text-color);
    font-size: 1rem;
}

/* --- 按钮样式 --- */
.btn {
    padding: 10px 20px;
    border-radius: 25px;
    text-decoration: none;
    color: var(--light-text-color);
    font-weight: bold;
    transition: all var(--transition-speed) ease;
    border: 2px solid transparent;
    cursor: pointer;
    font-size: 0.9rem;
}

.btn-login {
    background-color: var(--primary-color);
}

.btn-login:hover {
    background-color: var(--primary-hover-color);
    transform: translateY(-2px);
}

.btn-register {
    background-color: transparent;
    border-color: var(--light-text-color);
}

.btn-register:hover {
    background-color: var(--light-text-color);
    color: var(--primary-color);
}

.btn-logout {
    background-color: #dc3545;
}
.btn-logout:hover {
    background-color: #c82333;
}

/* --- 主内容区 --- */
.dashboard-content {
    flex-grow: 1; /* 占据剩余空间 */
    padding: 40px 20px;
    display: grid;
    /* 响应式网格布局: 自动填充，每列最小250px */
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 25px;
    position: relative;
    z-index: 2;
}

/* --- 功能大按钮 --- */
.feature-button {
    text-decoration: none;
    color: inherit;
    background-color: rgba(255, 255, 255, 0.92);
    border-radius: var(--border-radius);
    padding: 30px 20px;
    text-align: center;
    transition: all var(--transition-speed) ease;
    box-shadow: var(--box-shadow);
    border: 1px solid rgba(0, 0, 0, 0.05);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    min-height: 180px;
}

.feature-button:hover {
    transform: translateY(-8px) scale(1.02);
    box-shadow: 0 12px 25px rgba(0, 0, 0, 0.2);
    background-color: #ffffff;
}

.feature-button .icon {
    font-size: 3rem;
    color: var(--primary-color);
    margin-bottom: 15px;
}

.feature-button .text {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-color);
}

/* --- 登录后欢迎面板 --- */
.welcome-panel {
    grid-column: 1 / -1; /* 占满整行 */
    background: rgba(255, 255, 255, 0.92);
    padding: 30px;
    border-radius: var(--border-radius);
    text-align: center;
    box-shadow: var(--box-shadow);
}
.welcome-panel h2 {
    color: var(--primary-color);
    margin-bottom: 10px;
}
.logged-in-grid {
    margin-top: 30px;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
}

/* --- 页脚 --- */
.dashboard-footer {
    text-align: center;
    padding: 20px;
    background: rgba(0, 0, 0, 0.5);
    color: rgba(255, 255, 255, 0.7);
    font-size: 0.9rem;
    position: relative;
    z-index: 2;
}

.dashboard-footer a {
    color: var(--primary-color);
    text-decoration: none;
}

.dashboard-footer a:hover {
    text-decoration: underline;
}

/* --- 响应式设计 (小屏幕) --- */
@media (max-width: 768px) {
    .dashboard-header {
        padding: 10px 15px;
    }
    .logo span {
        font-size: 1.4rem;
    }
    .dashboard-content {
        padding: 20px 15px;
        grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
        gap: 15px;
    }
    .feature-button {
        padding: 20px 15px;
        min-height: 150px;
    }
    .feature-button .icon {
        font-size: 2.2rem;
    }
    .feature-button .text {
        font-size: 0.95rem;
    }
}