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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
    background-color: #f5f7fa;
    color: #333;
    min-height: 100vh;
}

:root {
    --primary: #2CB8A9;
    --primary-dark: #22a093;
    --primary-light: #e8f7f5;
    --text: #333;
    --text-light: #666;
    --text-lighter: #999;
    --border: #e4e7ed;
    --bg: #f5f7fa;
    --bg-white: #fff;
    --success: #67c23a;
    --warning: #e6a23c;
    --danger: #f56c6c;
}

.login-container {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: linear-gradient(135deg, #2CB8A9 0%, #1a9e90 100%);
}

.login-box {
    background: #fff;
    border-radius: 12px;
    padding: 40px;
    width: 400px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.15);
}

.login-header {
    text-align: center;
    margin-bottom: 30px;
}

.login-header h1 {
    color: var(--primary);
    font-size: 24px;
    margin-bottom: 8px;
}

.login-header p {
    color: var(--text-light);
    font-size: 14px;
}

.login-tabs {
    display: flex;
    margin-bottom: 24px;
    border-bottom: 2px solid var(--border);
}

.login-tab {
    flex: 1;
    padding: 12px 0;
    text-align: center;
    cursor: pointer;
    color: var(--text-light);
    font-size: 15px;
    border-bottom: 2px solid transparent;
    margin-bottom: -2px;
    transition: all 0.3s;
}

.login-tab.active {
    color: var(--primary);
    border-bottom-color: var(--primary);
}

.login-form {
    display: none;
}

.login-form.active {
    display: block;
}

.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 6px;
    color: var(--text-light);
    font-size: 14px;
}

.form-group input,
.form-group select,
.form-group textarea {
    width: 100%;
    padding: 10px 14px;
    border: 1px solid var(--border);
    border-radius: 8px;
    font-size: 14px;
    transition: border-color 0.3s;
    font-family: inherit;
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--primary);
}

.form-group textarea {
    resize: vertical;
    min-height: 80px;
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 10px 24px;
    border: none;
    border-radius: 8px;
    font-size: 14px;
    cursor: pointer;
    transition: all 0.3s;
    font-weight: 500;
    font-family: inherit;
}

.btn-primary {
    background: var(--primary);
    color: #fff;
    width: 100%;
    padding: 12px;
    font-size: 16px;
}

.btn-primary:hover {
    background: var(--primary-dark);
}

.btn-secondary {
    background: #f0f2f5;
    color: var(--text);
}

.btn-secondary:hover {
    background: #e4e7ed;
}

.btn-danger {
    background: var(--danger);
    color: #fff;
}

.btn-danger:hover {
    opacity: 0.9;
}

.btn-sm {
    padding: 6px 12px;
    font-size: 13px;
}

.btn-block {
    width: 100%;
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

.layout {
    display: flex;
    min-height: 100vh;
}

.sidebar {
    width: 240px;
    background: #1e2a38;
    color: #fff;
    flex-shrink: 0;
}

.sidebar-header {
    padding: 24px 20px;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.sidebar-header h2 {
    font-size: 18px;
    color: var(--primary);
    margin-bottom: 4px;
}

.sidebar-header p {
    font-size: 12px;
    color: rgba(255, 255, 255, 0.6);
}

.sidebar-nav {
    list-style: none;
    padding: 12px 0;
}

.sidebar-nav li {
    padding: 0;
}

.sidebar-nav a {
    display: flex;
    align-items: center;
    padding: 12px 20px;
    color: rgba(255, 255, 255, 0.7);
    text-decoration: none;
    font-size: 14px;
    transition: all 0.3s;
    border-left: 3px solid transparent;
}

.sidebar-nav a:hover,
.sidebar-nav a.active {
    background: rgba(255, 255, 255, 0.05);
    color: #fff;
    border-left-color: var(--primary);
}

.sidebar-nav .icon {
    margin-right: 12px;
    font-size: 18px;
    width: 20px;
    text-align: center;
}

.main {
    flex: 1;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

.topbar {
    background: #fff;
    padding: 16px 24px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--border);
}

.topbar-left h1 {
    font-size: 20px;
    color: var(--text);
}

.topbar-right {
    display: flex;
    align-items: center;
    gap: 16px;
}

.user-info {
    display: flex;
    align-items: center;
    gap: 8px;
}

.user-info .avatar {
    width: 36px;
    height: 36px;
    border-radius: 50%;
    background: var(--primary);
    color: #fff;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 14px;
    font-weight: 600;
}

.user-info .name {
    font-size: 14px;
    color: var(--text);
}

.user-info .role {
    font-size: 12px;
    color: var(--text-lighter);
}

.content {
    flex: 1;
    padding: 24px;
    overflow-y: auto;
}

.card {
    background: #fff;
    border-radius: 10px;
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.06);
    overflow: hidden;
    margin-bottom: 20px;
}

.card-header {
    padding: 16px 20px;
    border-bottom: 1px solid var(--border);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.card-header h3 {
    font-size: 16px;
    color: var(--text);
}

.card-body {
    padding: 20px;
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
    margin-bottom: 24px;
}

.stat-card {
    background: #fff;
    border-radius: 10px;
    padding: 24px;
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.06);
}

.stat-card .label {
    font-size: 14px;
    color: var(--text-light);
    margin-bottom: 8px;
}

.stat-card .value {
    font-size: 28px;
    font-weight: 600;
    color: var(--text);
}

.stat-card .primary .value {
    color: var(--primary);
}

.stat-card .warning .value {
    color: var(--warning);
}

.stat-card .danger .value {
    color: var(--danger);
}

.toolbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    gap: 16px;
    flex-wrap: wrap;
}

.toolbar-left {
    display: flex;
    gap: 12px;
    align-items: center;
    flex-wrap: wrap;
}

.search-box {
    position: relative;
}

.search-box input {
    width: 240px;
    padding: 8px 14px 8px 36px;
    border: 1px solid var(--border);
    border-radius: 8px;
    font-size: 14px;
}

.search-box input:focus {
    outline: none;
    border-color: var(--primary);
}

.search-box::before {
    content: "🔍";
    position: absolute;
    left: 12px;
    top: 50%;
    transform: translateY(-50%);
    font-size: 14px;
}

.filter-select {
    padding: 8px 14px;
    border: 1px solid var(--border);
    border-radius: 8px;
    font-size: 14px;
    background: #fff;
}

.data-table {
    width: 100%;
    border-collapse: collapse;
    background: #fff;
    border-radius: 10px;
    overflow: hidden;
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.06);
}

.data-table th,
.data-table td {
    padding: 14px 16px;
    text-align: left;
    border-bottom: 1px solid var(--border);
    font-size: 14px;
}

.data-table th {
    background: #f8f9fb;
    font-weight: 600;
    color: var(--text-light);
}

.data-table tr:hover td {
    background: #f8f9fb;
}

.data-table .actions {
    display: flex;
    gap: 8px;
}

.badge {
    display: inline-block;
    padding: 3px 10px;
    border-radius: 12px;
    font-size: 12px;
    font-weight: 500;
}

.badge-primary {
    background: var(--primary-light);
    color: var(--primary);
}

.badge-success {
    background: #f0f9eb;
    color: var(--success);
}

.badge-warning {
    background: #fdf6ec;
    color: var(--warning);
}

.badge-danger {
    background: #fef0f0;
    color: var(--danger);
}

.badge-default {
    background: #f4f4f5;
    color: var(--text-light);
}

.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    display: none;
    justify-content: center;
    align-items: center;
    z-index: 1000;
}

.modal-overlay.active {
    display: flex;
}

.modal {
    background: #fff;
    border-radius: 12px;
    width: 560px;
    max-width: 90%;
    max-height: 90vh;
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.modal-header {
    padding: 20px 24px;
    border-bottom: 1px solid var(--border);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.modal-header h3 {
    font-size: 18px;
}

.modal-close {
    background: none;
    border: none;
    font-size: 24px;
    cursor: pointer;
    color: var(--text-lighter);
    line-height: 1;
}

.modal-body {
    padding: 24px;
    overflow-y: auto;
    flex: 1;
}

.modal-footer {
    padding: 16px 24px;
    border-top: 1px solid var(--border);
    display: flex;
    justify-content: flex-end;
    gap: 12px;
}

.video-upload-area {
    border: 2px dashed var(--border);
    border-radius: 10px;
    padding: 30px;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s;
    margin-bottom: 16px;
}

.video-upload-area:hover,
.video-upload-area.dragover {
    border-color: var(--primary);
    background: var(--primary-light);
}

.video-upload-area .upload-icon {
    font-size: 48px;
    margin-bottom: 12px;
}

.video-upload-area .upload-text {
    color: var(--text-light);
    margin-bottom: 8px;
}

.video-upload-area .upload-hint {
    color: var(--text-lighter);
    font-size: 12px;
}

.video-preview {
    margin-top: 16px;
}

.video-preview video {
    width: 100%;
    max-height: 300px;
    border-radius: 8px;
    background: #000;
}

.video-info {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 8px;
    font-size: 13px;
    color: var(--text-light);
}

.form-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
}

.form-grid .full-width {
    grid-column: 1 / -1;
}

.empty-state {
    text-align: center;
    padding: 60px 20px;
    color: var(--text-lighter);
}

.empty-state .icon {
    font-size: 64px;
    margin-bottom: 16px;
}

.empty-state .text {
    font-size: 16px;
    margin-bottom: 8px;
}

.empty-state .hint {
    font-size: 14px;
}

.toast {
    position: fixed;
    top: 20px;
    left: 50%;
    transform: translateX(-50%);
    padding: 12px 24px;
    border-radius: 8px;
    color: #fff;
    font-size: 14px;
    z-index: 2000;
    opacity: 0;
    transition: opacity 0.3s;
}

.toast.show {
    opacity: 1;
}

.toast-success {
    background: var(--success);
}

.toast-error {
    background: var(--danger);
}

.toast-info {
    background: var(--primary);
}

.difficulty {
    color: var(--warning);
    letter-spacing: 2px;
}

.progress-bar {
    width: 100%;
    height: 6px;
    background: var(--border);
    border-radius: 3px;
    overflow: hidden;
    margin-top: 8px;
}

.progress-bar .progress {
    height: 100%;
    background: var(--primary);
    border-radius: 3px;
    transition: width 0.3s;
}

@media (max-width: 768px) {
    .form-grid {
        grid-template-columns: 1fr;
    }

    .sidebar {
        width: 64px;
    }

    .sidebar-header h2,
    .sidebar-header p,
    .sidebar-nav a span:not(.icon) {
        display: none;
    }

    .sidebar-nav a {
        justify-content: center;
    }

    .stats-grid {
        grid-template-columns: 1fr 1fr;
    }

    .search-box input {
        width: 160px;
    }
}

.modal-large {
    max-width: 800px;
    max-height: 90vh;
    overflow-y: auto;
}

.exercise-assign-section {
    margin-bottom: 24px;
}

.section-header-bar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding-bottom: 12px;
    border-bottom: 2px solid var(--primary-light);
    margin-bottom: 16px;
}

.section-title-bar {
    font-size: 16px;
    font-weight: 600;
    color: var(--text);
}

.count-badge {
    font-size: 13px;
    color: var(--primary);
    background: var(--primary-light);
    padding: 4px 12px;
    border-radius: 12px;
    font-weight: 500;
}

.current-exercises-list {
    display: flex;
    flex-direction: column;
    gap: 12px;
    max-height: 300px;
    overflow-y: auto;
}

.empty-state-inline {
    text-align: center;
    padding: 30px 20px;
    color: var(--text-lighter);
}

.empty-state-inline .empty-icon {
    font-size: 32px;
    display: block;
    margin-bottom: 8px;
}

.empty-state-inline .empty-text {
    font-size: 14px;
}

.exercise-assign-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 14px 16px;
    background: #f9fafb;
    border: 1px solid var(--border);
    border-radius: 8px;
    transition: all 0.2s;
}

.exercise-assign-item:hover {
    border-color: var(--primary);
    box-shadow: 0 2px 8px rgba(44, 184, 169, 0.1);
}

.exercise-assign-info {
    flex: 1;
    min-width: 0;
}

.exercise-assign-title {
    font-size: 15px;
    font-weight: 600;
    color: var(--text);
    margin-bottom: 8px;
    display: flex;
    align-items: center;
    gap: 6px;
}

.exercise-video-icon {
    color: var(--primary);
    font-size: 12px;
}

.exercise-assign-meta {
    display: flex;
    align-items: center;
    gap: 8px;
    flex-wrap: wrap;
}

.exercise-tag {
    font-size: 12px;
    color: var(--primary);
    background: var(--primary-light);
    padding: 2px 8px;
    border-radius: 4px;
}

.exercise-tag.difficulty-tag {
    color: var(--warning);
    background: #fdf6ec;
}

.exercise-meta-text {
    font-size: 12px;
    color: var(--text-lighter);
}

.exercise-assign-actions {
    display: flex;
    gap: 8px;
    flex-shrink: 0;
}

.exercise-add-section {
    border-top: 1px solid var(--border);
    padding-top: 20px;
}

.exercise-form {
    display: flex;
    flex-direction: column;
    gap: 14px;
}

.form-grid-2 {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 14px;
}

.form-grid-3 {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr;
    gap: 14px;
}

.badge-info {
    background: #e8f0ff;
    color: #45B7D1;
}

@media (max-width: 768px) {
    .form-grid-2,
    .form-grid-3 {
        grid-template-columns: 1fr;
    }

    .exercise-assign-item {
        flex-direction: column;
        align-items: stretch;
    }

    .exercise-assign-actions {
        justify-content: flex-end;
        margin-top: 10px;
    }
}