/* ============================================
   设计系统 — Design System
   轻题 · 轻量刷题平台
   ============================================ */

/* ----- CSS 变量（暗色主题默认） ----- */
:root {
    /* 颜色 */
    --color-bg: #080c18;
    --color-bg-secondary: #0e1428;
    --color-bg-card: #151d38;
    --color-bg-card-hover: #1a2342;
    --color-bg-input: #0c1124;
    --color-bg-overlay: rgba(0, 0, 0, 0.6);
    --color-border: #1e2d5a;
    --color-border-focus: #818cf8;
    --color-border-hover: #2d3f6e;

    --color-text: #eef0f7;
    --color-text-secondary: #a5b0cf;
    --color-text-muted: #6b7aa8;

    --color-primary: #818cf8;
    --color-primary-hover: #6d78f0;
    --color-primary-light: rgba(129, 140, 248, 0.12);
    --color-primary-glow: rgba(129, 140, 248, 0.25);

    --color-accent: #f59e0b;
    --color-accent-light: rgba(245, 158, 11, 0.12);

    --color-success: #34d399;
    --color-success-light: rgba(52, 211, 153, 0.12);
    --color-warning: #fbbf24;
    --color-warning-light: rgba(251, 191, 36, 0.12);
    --color-danger: #f87171;
    --color-danger-light: rgba(248, 113, 113, 0.12);
    --color-info: #60a5fa;
    --color-info-light: rgba(96, 165, 250, 0.12);

    /* 渐变 */
    --gradient-primary: linear-gradient(135deg, #818cf8 0%, #a78bfa 50%, #c084fc 100%);
    --gradient-success: linear-gradient(135deg, #059669 0%, #34d399 100%);
    --gradient-danger: linear-gradient(135deg, #dc2626 0%, #f87171 100%);
    --gradient-card: linear-gradient(145deg, rgba(21, 29, 56, 0.92) 0%, rgba(14, 20, 40, 0.96) 100%);

    /* 排版 */
    --font-sans: 'Inter', 'Noto Sans SC', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', 'Consolas', monospace;

    /* 圆角 */
    --radius-sm: 8px;
    --radius-md: 14px;
    --radius-lg: 20px;
    --radius-xl: 28px;
    --radius-full: 9999px;

    /* 阴影 — 暗色 */
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.3);
    --shadow-md: 0 4px 12px rgba(0,0,0,0.35), 0 2px 4px rgba(0,0,0,0.2);
    --shadow-lg: 0 12px 28px rgba(0,0,0,0.45), 0 4px 10px rgba(0,0,0,0.25);
    --shadow-xl: 0 24px 40px rgba(0,0,0,0.55), 0 8px 16px rgba(0,0,0,0.3);
    --shadow-glow: 0 0 30px var(--color-primary-glow);
    --shadow-accent: 0 0 24px rgba(245, 158, 11, 0.15);

    /* 过渡 */
    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 400ms cubic-bezier(0.4, 0, 0.2, 1);
}

/* ----- 亮色主题 ----- */
[data-theme="light"] {
    --color-bg: #f0f2f8;
    --color-bg-secondary: #ffffff;
    --color-bg-card: #ffffff;
    --color-bg-card-hover: #f5f7fd;
    --color-bg-input: #ffffff;
    --color-bg-overlay: rgba(0, 0, 0, 0.25);
    --color-border: #dce1f0;
    --color-border-focus: #6366f1;
    --color-border-hover: #c5cde0;

    --color-text: #121826;
    --color-text-secondary: #4b5580;
    --color-text-muted: #8b95b8;

    --color-primary: #6366f1;
    --color-primary-hover: #5558e6;
    --color-primary-light: rgba(99, 102, 241, 0.08);
    --color-primary-glow: rgba(99, 102, 241, 0.15);

    --color-accent: #d97706;
    --color-accent-light: rgba(217, 119, 6, 0.08);

    --color-success: #059669;
    --color-success-light: rgba(5, 150, 105, 0.08);
    --color-danger: #dc2626;
    --color-danger-light: rgba(220, 38, 38, 0.08);

    --shadow-sm: 0 1px 3px rgba(0,0,0,0.05);
    --shadow-md: 0 4px 12px rgba(0,0,0,0.07), 0 2px 4px rgba(0,0,0,0.04);
    --shadow-lg: 0 12px 28px rgba(0,0,0,0.09), 0 4px 10px rgba(0,0,0,0.05);
    --shadow-xl: 0 24px 40px rgba(0,0,0,0.11), 0 8px 16px rgba(0,0,0,0.06);
}

/* ----- 基础重置 ----- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html {
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    overscroll-behavior: none;
    -webkit-overflow-scrolling: touch;
}

body {
    font-family: var(--font-sans);
    background: var(--color-bg);
    color: var(--color-text);
    line-height: 1.6;
    min-height: 100vh;
    overscroll-behavior: none;
    transition: background var(--transition-base), color var(--transition-base);
    padding-bottom: 56px;
}
@media (max-width: 640px) {
    body { padding-bottom: 0; }
}

a { color: var(--color-primary); text-decoration: none; transition: color var(--transition-fast); }
a:hover { color: var(--color-primary-hover); }
a:focus-visible { outline: 2px solid var(--color-primary); outline-offset: 2px; border-radius: 2px; }

/* Focus 可见环（键盘导航） */
:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
    border-radius: 4px;
}
:focus:not(:focus-visible) { outline: none; }

/* ----- 排版 ----- */
h1 { font-size: 2.5rem; font-weight: 800; letter-spacing: -0.025em; line-height: 1.2; }
h2 { font-size: 1.5rem; font-weight: 700; letter-spacing: -0.01em; }
h3 { font-size: 1.2rem; font-weight: 600; }

@media (max-width: 640px) {
    h1 { font-size: 1.75rem; }
    h2 { font-size: 1.25rem; }
}

/* ----- 按钮系统 ----- */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px 24px;
    min-height: 44px;
    border: none;
    border-radius: var(--radius-md);
    font-family: var(--font-sans);
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
    position: relative;
    overflow: hidden;
    white-space: nowrap;
    user-select: none;
    -webkit-tap-highlight-color: transparent;
}
.btn:active { transform: scale(0.97); }
.btn:disabled { opacity: 0.5; cursor: not-allowed; transform: none; }

.btn-primary {
    background: var(--gradient-primary);
    color: #fff;
    box-shadow: 0 4px 20px var(--color-primary-glow);
}
.btn-primary:hover:not(:disabled) {
    box-shadow: 0 6px 30px var(--color-primary-glow);
    transform: translateY(-2px);
}
.btn-primary:active:not(:disabled) {
    box-shadow: 0 2px 10px var(--color-primary-glow);
    transform: scale(0.97) translateY(0);
}

.btn-outline {
    background: transparent;
    color: var(--color-text-secondary);
    border: 1.5px solid var(--color-border);
}
.btn-outline:hover:not(:disabled) {
    border-color: var(--color-border-focus);
    color: var(--color-text);
    background: var(--color-primary-light);
}
.btn-outline:active:not(:disabled) {
    background: var(--color-primary-light);
    transform: scale(0.97);
}

.btn-danger {
    background: var(--gradient-danger);
    color: #fff;
}
.btn-danger:hover:not(:disabled) {
    box-shadow: 0 4px 20px rgba(248, 113, 113, 0.3);
    transform: translateY(-2px);
}
.btn-danger:active:not(:disabled) {
    box-shadow: 0 2px 10px rgba(248, 113, 113, 0.2);
    transform: scale(0.97) translateY(0);
}

.btn-danger-outline {
    color: var(--color-danger);
    border-color: rgba(248, 113, 113, 0.25);
}
.btn-danger-outline:hover:not(:disabled) {
    background: var(--color-danger-light);
    border-color: var(--color-danger);
}
.btn-danger-outline:active:not(:disabled) {
    background: var(--color-danger-light);
    transform: scale(0.97);
}

.btn-warning {
    background: linear-gradient(135deg, #fbbf24, #f59e0b);
    color: #1a1a2e;
}
.btn-warning:hover:not(:disabled) {
    box-shadow: 0 4px 20px rgba(251, 191, 36, 0.3);
    transform: translateY(-2px);
}
.btn-warning:active:not(:disabled) {
    box-shadow: 0 2px 10px rgba(251, 191, 36, 0.2);
    transform: scale(0.97) translateY(0);
}

.btn-success {
    background: var(--gradient-success);
    color: #fff;
}
.btn-success:hover:not(:disabled) {
    box-shadow: 0 4px 20px rgba(52, 211, 153, 0.3);
    transform: translateY(-2px);
}
.btn-success:active:not(:disabled) {
    box-shadow: 0 2px 10px rgba(52, 211, 153, 0.2);
    transform: scale(0.97) translateY(0);
}

.btn-lg { padding: 16px 36px; min-height: 52px; font-size: 1.1rem; border-radius: var(--radius-lg); }
.btn-sm { padding: 8px 16px; min-height: 36px; font-size: 0.82rem; border-radius: var(--radius-sm); }
@media (max-width: 640px) {
    .btn-lg { padding: 14px 24px; min-height: 48px; font-size: 1rem; }
}

.btn svg { flex-shrink: 0; }

/* ----- 表单 ----- */
.form-group { display: flex; flex-direction: column; gap: 6px; }
.form-group label {
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--color-text-secondary);
}
.form-row {
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
}
@media (max-width: 640px) {
    .form-row { flex-direction: column; }
}

select, .input {
    padding: 14px 18px;
    min-height: 48px;
    border: 1.5px solid var(--color-border);
    border-radius: var(--radius-md);
    font-family: var(--font-sans);
    font-size: 0.95rem;
    background: var(--color-bg-input);
    color: var(--color-text);
    transition: all var(--transition-fast);
    outline: none;
    min-width: 180px;
    -webkit-tap-highlight-color: transparent;
}
select:hover, .input:hover { border-color: var(--color-border-hover); }
select:focus, .input:focus {
    border-color: var(--color-border-focus);
    box-shadow: 0 0 0 4px var(--color-primary-light);
}
select:focus-visible, .input:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 1px;
}
select { cursor: pointer; appearance: none; background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%239ca3af' stroke-width='2.5'%3E%3Cpolyline points='6 9 12 15 18 9'/%3E%3C/svg%3E"); background-repeat: no-repeat; background-position: right 12px center; padding-right: 36px; }

/* ----- 主题切换按钮 ----- */
.theme-toggle {
    position: fixed;
    top: 16px;
    right: 16px;
    z-index: 1000;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    border: 1.5px solid var(--color-border);
    background: var(--color-bg-card);
    color: var(--color-text-secondary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
    backdrop-filter: blur(10px);
    -webkit-tap-highlight-color: transparent;
    user-select: none;
}
.theme-toggle:hover {
    border-color: var(--color-border-focus);
    color: var(--color-text);
    box-shadow: var(--shadow-md);
}
.theme-toggle:active {
    transform: scale(0.92);
}
@media (max-width: 640px) {
    .theme-toggle { top: 12px; right: 12px; width: 40px; height: 40px; }
}
[data-theme="dark"] .icon-sun { display: block; }
[data-theme="dark"] .icon-moon { display: none; }
[data-theme="light"] .icon-sun { display: none; }
[data-theme="light"] .icon-moon { display: block; }

/* ----- Modal ----- */
.modal-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: var(--color-bg-overlay);
    backdrop-filter: blur(8px);
    z-index: 2000;
    align-items: center;
    justify-content: center;
    padding: 20px;
}
.modal-overlay.show { display: flex; }

.modal {
    background: var(--color-bg-card);
    border-radius: var(--radius-xl);
    border: 1px solid var(--color-border);
    padding: 32px;
    max-width: 480px;
    width: 100%;
    box-shadow: var(--shadow-xl);
    animation: modalIn 0.25s ease-out;
    max-height: 90vh;
    overflow-y: auto;
}
@keyframes modalIn {
    from { opacity: 0; transform: scale(0.95) translateY(12px); }
    to { opacity: 1; transform: scale(1) translateY(0); }
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
}
.modal-header h3 { margin: 0; }
.modal-close {
    background: none;
    border: none;
    color: var(--color-text-muted);
    cursor: pointer;
    padding: 8px;
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
    display: flex;
    -webkit-tap-highlight-color: transparent;
}
.modal-close:hover { color: var(--color-text); background: var(--color-bg-card-hover); }
.modal-close:active { transform: scale(0.9); }

.modal-body { margin-bottom: 24px; }
.modal-body p { color: var(--color-text-secondary); margin-bottom: 12px; }

.modal-footer { display: flex; justify-content: flex-end; gap: 12px; }
@media (max-width: 640px) {
    .modal { padding: 24px; border-radius: var(--radius-lg); }
}

/* ----- Toast ----- */
.toast-container {
    position: fixed;
    top: 20px;
    right: 20px;
    z-index: 3000;
    display: flex;
    flex-direction: column;
    gap: 10px;
    pointer-events: none;
}
.toast {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 14px 20px;
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    font-size: 0.9rem;
    font-weight: 500;
    pointer-events: auto;
    animation: toastIn 0.3s ease-out;
    max-width: 420px;
    min-height: 50px;
}
@media (max-width: 640px) {
    .toast-container { top: 12px; right: 12px; left: 12px; }
    .toast { max-width: 100%; font-size: 0.85rem; padding: 12px 16px; }
}
.toast.removing { animation: toastOut 0.2s ease-in forwards; }
.toast-success { border-left: 3px solid var(--color-success); }
.toast-error { border-left: 3px solid var(--color-danger); }
.toast-warning { border-left: 3px solid var(--color-warning); }
.toast-info { border-left: 3px solid var(--color-info); }

@keyframes toastIn {
    from { opacity: 0; transform: translateX(100%); }
    to { opacity: 1; transform: translateX(0); }
}
@keyframes toastOut {
    from { opacity: 1; transform: translateX(0); }
    to { opacity: 0; transform: translateX(100%); }
}

/* ----- Spinner ----- */
.spinner {
    width: 36px;
    height: 36px;
    border: 3px solid var(--color-border);
    border-top-color: var(--color-primary);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ----- 空状态 ----- */
.empty-state {
    text-align: center;
    padding: 48px 24px;
    color: var(--color-text-muted);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 12px;
}
.empty-state p { font-size: 1.1rem; font-weight: 500; color: var(--color-text-secondary); }
.empty-state span { font-size: 0.9rem; color: var(--color-text-muted); }

/* ----- 响应式容器 ----- */
.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 20px;
}

/* ----- 滚动条美化 ----- */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--color-border); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: var(--color-text-muted); }
body { scrollbar-width: thin; scrollbar-color: var(--color-border) transparent; }

/* ----- 选中颜色 ----- */
::selection { background: var(--color-primary-light); color: var(--color-text); }

/* ----- 站点页脚（ICP备案 + 公安备案） ----- */
.site-footer {
    text-align: center;
    padding: 14px 20px;
    font-size: 0.78rem;
    color: var(--color-text-muted);
    background: var(--color-bg-secondary);
    border-top: 1px solid var(--color-border);
    position: fixed;
    bottom: 0;
    left: 0;
    width: 100%;
    z-index: 50;
    backdrop-filter: blur(12px);
}
.site-footer a {
    color: var(--color-text-muted);
    text-decoration: none;
    transition: color var(--transition-fast);
}
.site-footer a:hover {
    color: var(--color-primary);
}
.footer-sep {
    margin: 0 10px;
    color: var(--color-border);
}
.gongan-icon {
    width: 14px;
    height: 14px;
    vertical-align: -2px;
    margin-right: 3px;
}
@media (max-width: 640px) {
    .site-footer {
        padding: 10px 16px;
        font-size: 0.65rem;
        backdrop-filter: none;
    }
    .footer-sep { margin: 0 4px; }
}