/* ========== CSS Variables - 子木品牌色系 ========== */
:root {
    /* 主色 - 子木绿 */
    --color-primary:       #4abc99;
    --color-primary-light: #78d4b6;
    --color-primary-dark:  #3aa383;

    /* 强调色 - 珊瑚橙 */
    --color-accent:        #ff8f60;
    --color-accent-dark:   #e67a4d;

    /* 背景色 */
    --color-bg-page:       #f7fafa;
    --color-bg-card:       #ffffff;
    --color-bg-sidebar:    #eef8f4;

    /* 文字色 */
    --color-text-primary:   #434959;
    --color-text-secondary: #6b7280;
    --color-text-muted:     #9ca3af;

    /* 边框 */
    --color-border:        #d1d5db;
    --color-border-light:  #e5e7eb;
    --color-border-hover:  #b7b7b7;

    /* 语义色 */
    --color-success:       #22C55E;
    --color-success-bg:    #F0FDF4;
    --color-warning:       #F59E0B;
    --color-warning-bg:    #FFFBEB;
    --color-error:         #EF4444;
    --color-error-bg:      #FEF2F2;
    --color-danger:        #EF4444;
    --color-info:          #3B82F6;
    --color-info-bg:       #EFF6FF;

    /* 字体 - 与 zimuedu.com 一致 */
    --font-sans:  "Helvetica Neue", Helvetica, "PingFang SC", "Noto Sans SC", "Microsoft YaHei", Arial, sans-serif;
    --font-mono:  'SF Mono', 'Monaco', 'Menlo', monospace;

    /* 导航栏高度 */
    --navbar-height: 56px;

    /* 圆角 */
    --radius-sm:   6px;
    --radius-md:   10px;
    --radius-lg:   14px;
    --radius-xl:   20px;
    --radius-full: 9999px;

    /* 阴影 */
    --shadow-sm:    0 1px 3px rgba(0, 0, 0, 0.06);
    --shadow-md:    0 4px 8px rgba(0, 0, 0, 0.06);
    --shadow-lg:    0 10px 25px rgba(0, 0, 0, 0.08);
    --shadow-hover: 0 4px 12px rgba(74, 188, 153, 0.18);

    /* 间距 */
    --space-1: 4px;
    --space-2: 8px;
    --space-3: 12px;
    --space-4: 16px;
    --space-5: 20px;
    --space-6: 24px;
    --space-8: 32px;
    --space-10: 40px;

    /* z-index 层级 */
    --z-dropdown: 100;
    --z-sticky:   200;
    --z-overlay:  500;
    --z-modal:    1000;
    --z-toast:    1100;
}

/* ========== 全局样式 ========== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html, body {
    height: 100%;
    width: 100%;
}

body {
    font-family: var(--font-sans);
    font-size: 16px;
    line-height: 1.6;
    color: var(--color-text-primary);
    background: var(--color-bg-page);
}

/* ========== 工具类 ========== */
.hidden { display: none !important; }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }

/* ========== 导航栏 ========== */
.navbar {
    background: #4abc99;
    border-bottom: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: var(--z-sticky);
    box-shadow: 0 2px 6px rgba(0,0,0,.08);
}

.navbar-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 var(--space-6);
    height: var(--navbar-height);
}

.navbar-brand {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    font-weight: 600;
    font-size: 17px;
    color: #ffffff;
    text-decoration: none;
    cursor: pointer;
}

.navbar-brand:hover {
    opacity: 0.9;
}

.brand-icon {
    width: 42px;
    height: 42px;
    object-fit: contain;
    flex-shrink: 0;
    background: #ffffff;
    border-radius: 10px;
    padding: 4px;
}

.brand-text {
    display: flex;
    flex-direction: column;
    line-height: 1.2;
}

.brand-name {
    font-size: inherit;
}

.brand-slogan {
    font-size: 11px;
    font-weight: 400;
    opacity: 0.7;
    letter-spacing: 1px;
}

.navbar-menu {
    display: flex;
    align-items: center;
    gap: var(--space-5);
}

.navbar-user {
    font-size: 14px;
    color: #ffffff;
    display: flex;
    align-items: center;
    gap: var(--space-2);
    background: rgba(255,255,255,.2);
    padding: 6px 12px;
    border-radius: 20px;
    font-weight: 500;
}

.navbar-user .icon-sm {
    width: 16px;
    height: 16px;
    color: #ffffff;
}

.navbar-link {
    font-size: 14px;
    font-weight: 500;
    color: #ffffff;
    text-decoration: none;
    padding: 6px 14px;
    border-radius: 6px;
    border: 1px solid rgba(255,255,255,.35);
    background: transparent;
    transition: all 0.2s ease;
}

.navbar-link:hover {
    color: #ffffff;
    border-color: rgba(255,255,255,.6);
    background: rgba(255,255,255,.15);
}

.navbar-link-logout {
    color: rgba(255,255,255,.7);
    border-color: transparent;
    background: transparent;
}

.navbar-link-logout:hover {
    color: #fff;
    border-color: transparent;
    background: rgba(255,255,255,.15);
}

.navbar-link:focus-visible {
    outline: 2px solid #fff;
    outline-offset: 2px;
}

.badge-admin {
    background: rgba(255,255,255,.25);
    color: #ffffff;
    padding: 2px 6px;
    border-radius: 3px;
    font-size: 11px;
    font-weight: 600;
}

.badge-supervisor {
    background: rgba(255,255,255,.2);
    color: #FEF3C7;
    padding: 2px 6px;
    border-radius: 3px;
    font-size: 11px;
    font-weight: 600;
}

/* ========== 主内容区 ========== */
.main-content {
    flex: 1;
    min-height: calc(100vh - 120px);
    padding-top: var(--navbar-height);
}

.footer {
    text-align: center;
    padding: var(--space-6);
    color: #8a8f93;
    font-size: 15px;
    border-top: none;
    background: transparent;
}

/* ========== 按钮 ========== */
.btn {
    display: inline-block;
    padding: 10px 24px;
    border-radius: 8px;
    font-size: 16px;
    font-weight: 500;
    border: none;
    cursor: pointer;
    text-decoration: none;
    text-align: center;
    transition: background 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}

.btn:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

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

.btn-primary:hover {
    background: var(--color-primary-dark);
    box-shadow: var(--shadow-md);
}

.btn-primary:disabled {
    background: #d1d5db;
    cursor: not-allowed;
}

.btn-secondary {
    background: transparent;
    color: var(--color-text-secondary);
    border: 1px solid var(--color-border);
}

.btn-secondary:hover {
    border-color: var(--color-primary);
    color: var(--color-primary);
}

.btn-danger {
    background: var(--color-error);
    color: white;
}

.btn-danger:hover {
    background: #DC2626;
}

/* ========== 表单 ========== */
.form-group {
    margin-bottom: var(--space-5);
}

.form-label {
    display: block;
    font-size: 15px;
    font-weight: 500;
    color: var(--color-text-primary);
    margin-bottom: var(--space-2);
}

.form-control {
    width: 100%;
    padding: 10px 14px;
    border: 1px solid var(--color-border);
    border-radius: 8px;
    font-size: 16px;
    font-family: var(--font-sans);
    color: var(--color-text-primary);
    background: white;
    transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.form-control:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(74, 188, 153, 0.2);
}

.form-control:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: -2px;
}

.form-control::placeholder {
    color: var(--color-text-muted);
}

/* ========== 表格 ========== */
.table {
    width: 100%;
    border-collapse: separate;
    border-spacing: 0;
}

.table th {
    background: var(--color-bg-sidebar);
    padding: 12px 16px;
    font-weight: 600;
    font-size: 15px;
    color: var(--color-text-secondary);
    text-align: left;
    border-bottom: 1px solid var(--color-border);
}

.table td {
    padding: 14px 16px;
    border-bottom: 1px solid var(--color-border);
    font-size: 15px;
}

.table tr:hover td {
    background: var(--color-bg-page);
}

.table tr:last-child td {
    border-bottom: none;
}

.table-container {
    overflow-x: auto;
}

/* ========== 卡片 ========== */
.card {
    background: var(--color-bg-card);
    border-radius: var(--radius-md);
    padding: var(--space-5);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--color-border-light);
    transition: box-shadow 0.2s ease;
}

.card:hover {
    box-shadow: var(--shadow-hover);
}

.card-subject {
    border-radius: var(--radius-xl);
    padding: var(--space-6);
    text-align: center;
    cursor: pointer;
}

.card-subject:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-hover);
}

.card-subject.active {
    border-color: var(--color-primary);
    background: var(--color-bg-page);
    box-shadow: 0 0 0 2px var(--color-primary-light);
}

/* ========== Badge ========== */
.badge {
    display: inline-flex;
    align-items: center;
    gap: var(--space-2);
    padding: 4px 10px;
    border-radius: var(--radius-full);
    font-size: 14px;
    font-weight: 500;
}

.badge-success {
    background: #DCFCE7;
    color: #166534;
}

.badge-info {
    background: #DBEAFE;
    color: #1E40AF;
}

.badge-warning {
    background: #FEF3C7;
    color: #92400E;
}

.badge-error {
    background: #FEE2E2;
    color: #991B1B;
}

.badge-neutral {
    background: #F3F4F6;
    color: #374151;
}

/* ========== Unified Product Badges ========== */
.ui-badge {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 24px;
    padding: 0 10px;
    border-radius: var(--radius-full);
    font-size: 11px;
    font-weight: 800;
    letter-spacing: .02em;
    line-height: 1;
    white-space: nowrap;
    border: 1px solid transparent;
    box-shadow: inset 0 1px 0 rgba(255,255,255,.55);
}

.ui-badge--subject {
    min-width: 48px;
}

.ui-badge--status {
    min-height: 26px;
    padding: 0 12px;
    font-size: 12px;
    font-weight: 900;
    letter-spacing: .01em;
}

.ui-badge--success {
    min-height: 28px;
    padding: 0 12px;
    font-size: 12px;
    font-weight: 900;
    letter-spacing: .04em;
}

.ui-badge--toefl {
    background: #eff6ff;
    color: #1d4ed8;
    border-color: #bfdbfe;
}

.ui-badge--ielts {
    background: #fdf2f8;
    color: #be185d;
    border-color: #f9a8d4;
}

.ui-badge--sat {
    background: #f5f3ff;
    color: #7c3aed;
    border-color: #d8b4fe;
}

.ui-badge--free {
    background: #ecfdf5;
    color: #0f766e;
    border-color: #a7f3d0;
}

.ui-badge--member {
    background: #fffbeb;
    color: #b45309;
    border-color: #fde68a;
}

.ui-badge--student {
    background: #eff6ff;
    color: #1d4ed8;
    border-color: #bfdbfe;
}

/* ========== Toast 通知 ========== */
.toast-container {
    position: fixed;
    top: calc(var(--navbar-height) + 16px);
    right: 16px;
    z-index: var(--z-toast);
    display: flex;
    flex-direction: column;
    gap: 8px;
    pointer-events: none;
}

.toast {
    pointer-events: auto;
    padding: 12px 20px;
    border-radius: 8px;
    font-size: 15px;
    font-weight: 500;
    box-shadow: var(--shadow-lg);
    animation: toastIn 0.3s ease;
    max-width: 360px;
}

.toast-warning {
    background: var(--color-warning-bg);
    color: #92400E;
    border: 1px solid #FDE68A;
}

.toast-error {
    background: var(--color-error-bg);
    color: #991B1B;
    border: 1px solid #FECACA;
}

.toast-success {
    background: var(--color-success-bg);
    color: #166534;
    border: 1px solid #BBF7D0;
}

.toast-info {
    background: var(--color-info-bg);
    color: #1E40AF;
    border: 1px solid #BFDBFE;
}

.toast.fade-out {
    animation: toastOut 0.3s ease forwards;
}

@keyframes toastIn {
    from { opacity: 0; transform: translateX(40px); }
    to   { opacity: 1; transform: translateX(0); }
}

@keyframes toastOut {
    from { opacity: 1; transform: translateX(0); }
    to   { opacity: 0; transform: translateX(40px); }
}

/* ========== Skeleton 加载占位 ========== */
.skeleton {
    background: linear-gradient(90deg, #e5e7eb 25%, #f3f4f6 50%, #e5e7eb 75%);
    background-size: 200% 100%;
    animation: shimmer 1.5s infinite;
    border-radius: var(--radius-sm);
}

@keyframes shimmer {
    0%   { background-position: 200% 0; }
    100% { background-position: -200% 0; }
}

/* ========== 图标尺寸 ========== */
.icon-sm  { width: 16px; height: 16px; flex-shrink: 0; }
.icon-md  { width: 20px; height: 20px; flex-shrink: 0; }
.icon-lg  { width: 24px; height: 24px; flex-shrink: 0; }

/* ========== 动画 ========== */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(8px); }
    to   { opacity: 1; transform: translateY(0); }
}

.page-enter {
    animation: fadeIn 0.3s ease;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* ========== prefers-reduced-motion ========== */
@media (prefers-reduced-motion: reduce) {
    *, *::before, *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* ========== 响应式设计 ========== */

/* 大屏外接显示器 */
@media (min-width: 1920px) {
    body {
        font-size: 17px;
    }
}

/* 平板竖屏：导航栏缩小但保持水平 */
@media (max-width: 768px) {
    .navbar {
        position: sticky;
    }
    .main-content {
        padding-top: 0;
    }
    .navbar-container {
        padding: 0 var(--space-3);
    }
    .brand-icon {
        width: 38px;
        height: 38px;
        border-radius: 9px;
    }
    .brand-name {
        font-size: 14px;
    }
    .brand-slogan {
        font-size: 10px;
    }
    .navbar-menu {
        gap: var(--space-3);
    }
    .navbar-link {
        font-size: 13px;
        padding: 5px 10px;
    }
    .navbar-user {
        font-size: 13px;
        padding: 5px 10px;
    }
    .table {
        font-size: 13px;
    }
    .table th, .table td {
        padding: 8px 12px;
    }
}

/* 手机：导航栏纵向堆叠 */
@media (max-width: 480px) {
    .navbar {
        position: sticky;
    }
    .main-content {
        padding-top: 0;
    }
    .navbar-container {
        flex-direction: column;
        height: auto;
        padding: var(--space-3);
        gap: var(--space-2);
    }
    .navbar-brand {
        width: 100%;
    }
    .brand-icon {
        width: 36px;
        height: 36px;
        border-radius: 9px;
    }
    .brand-name {
        font-size: 13px;
    }
    .brand-slogan {
        display: none;
    }
    .navbar-menu {
        width: 100%;
        justify-content: space-between;
        flex-wrap: wrap;
        gap: var(--space-2);
    }
    .navbar-link {
        font-size: 13px;
        padding: 6px 10px;
    }
}

/* 组合练习悬浮导航：由 practice_nav.js 注入，样式集中在外部 CSS 以满足严格 CSP。 */
.combo-bar {
    position: fixed;
    left: 20px;
    bottom: 20px;
    z-index: 10000;
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 6px;
    max-width: min(560px, calc(100vw - 40px));
    padding: 6px 14px;
    font-size: 0.75rem;
    color: #fff;
    background: rgba(67, 73, 89, 0.92);
    backdrop-filter: blur(8px);
    border-radius: 20px;
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.2);
    font-family: inherit;
    cursor: grab;
    user-select: none;
    transition: box-shadow 0.15s;
}

.combo-step {
    white-space: nowrap;
}

.combo-bar.is-dragging {
    cursor: grabbing;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
}

.combo-step.is-current {
    font-weight: 700;
    text-decoration: underline;
}

.combo-step.is-done {
    opacity: 0.6;
    text-decoration: line-through;
}

.combo-step.is-pending {
    opacity: 0.5;
}

.combo-step-separator {
    opacity: 0.35;
}

.combo-exit-btn {
    margin-left: 2px;
    padding: 1px 8px;
    border: 1px solid rgba(255, 255, 255, 0.35);
    border-radius: 10px;
    background: transparent;
    color: #fff;
    font-size: 0.7rem;
    cursor: pointer;
    font-family: inherit;
    transition: all 0.15s;
    line-height: 1.6;
}

.combo-exit-btn:hover {
    background: rgba(239, 68, 68, 0.8);
    border-color: rgba(239, 68, 68, 0.8);
}

.combo-overlay {
    position: fixed;
    inset: 0;
    z-index: 10000;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    background: rgba(255, 255, 255, 0.95);
}

.combo-overlay-icon {
    font-size: 2.5rem;
    margin-bottom: 16px;
}

.combo-overlay-title {
    font-size: 1.2rem;
    font-weight: 600;
    color: #333;
    margin-bottom: 8px;
}

.combo-overlay-title-spaced {
    margin-bottom: 12px;
}

.combo-overlay-copy {
    font-size: 1rem;
    color: #888;
    margin-bottom: 20px;
}

.combo-overlay-subcopy {
    font-size: 0.9rem;
    color: #888;
}

.combo-overlay-actions {
    display: flex;
    gap: 12px;
}

.combo-overlay-btn {
    padding: 10px 28px;
    border: none;
    border-radius: 10px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    font-family: inherit;
}

.combo-overlay-btn-primary {
    background: #ff8f60;
    color: #fff;
}

.combo-overlay-btn-secondary {
    background: #ddd;
    color: #666;
}