/* ===== Flutter-like Material Design ===== */
:root {
    --primary: #1a73e8;
    --primary-dark: #0d47a1;
    --surface: #ffffff;
    --background: #f5f7fa;
    --text: #202124;
    --text-secondary: #5f6368;
    --border: #dadce0;
    --shadow: 0 2px 8px rgba(0,0,0,0.08), 0 1px 2px rgba(0,0,0,0.06);
    --radius: 12px;
    --radius-btn: 24px;
    --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

@media (prefers-color-scheme: dark) {
    :root {
        --surface: #1e1e1e;
        --background: #121212;
        --text: #e8eaed;
        --text-secondary: #9aa0a6;
        --border: #3c4043;
        --shadow: 0 2px 8px rgba(0,0,0,0.3);
        --primary: #8ab4f8;
        --primary-dark: #5b9bd5;
    }
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background: var(--background);
    color: var(--text);
    line-height: 1.6;
    padding: 24px 16px;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    transition: background 0.3s, color 0.3s;
}

/* 容器 – 类似 Flutter 的 Scaffold */
.container {
    max-width: 800px;
    width: 100%;
    margin: 0 auto;
}

/* ===== 卡片 ===== */
.card {
    background: var(--surface);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 24px;
    margin-bottom: 24px;
    transition: background 0.3s, box-shadow 0.3s;
}

/* ===== 导航栏 – 类似 AppBar ===== */
.app-bar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 0;
    border-bottom: 1px solid var(--border);
    margin-bottom: 28px;
    flex-wrap: wrap;
    gap: 12px;
}

.app-bar .brand {
    font-size: 1.8rem;
    font-weight: 500;
    letter-spacing: -0.5px;
    color: var(--text);
}

.app-bar .brand small {
    font-size: 0.9rem;
    font-weight: 400;
    color: var(--text-secondary);
    margin-left: 8px;
}

.app-bar nav {
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
}

.app-bar nav a {
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.95rem;
    font-weight: 500;
    padding: 6px 0;
    border-bottom: 2px solid transparent;
    transition: color 0.2s, border-color 0.2s;
}

.app-bar nav a:hover {
    color: var(--text);
}

.app-bar nav a.active {
    color: var(--primary);
    border-bottom-color: var(--primary);
}

/* ===== 按钮 – 类似 Flutter Elevated/Outlined ===== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 10px 24px;
    border-radius: var(--radius-btn);
    font-size: 0.95rem;
    font-weight: 500;
    text-decoration: none;
    border: none;
    background: transparent;
    color: var(--primary);
    cursor: pointer;
    transition: background 0.2s, box-shadow 0.2s, transform 0.1s;
    box-shadow: none;
    min-height: 44px;
}

.btn-primary {
    background: var(--primary);
    color: #fff;
    box-shadow: 0 2px 4px rgba(26,115,232,0.3);
}

.btn-primary:hover {
    background: var(--primary-dark);
    box-shadow: 0 4px 8px rgba(26,115,232,0.4);
    transform: translateY(-1px);
}

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

.btn-outline:hover {
    background: rgba(0,0,0,0.04);
}

.btn:active {
    transform: scale(0.97);
}

/* ===== 表单 – 类似 Flutter TextField ===== */
.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--text-secondary);
    margin-bottom: 4px;
}

.form-group input {
    width: 100%;
    max-width: 360px;
    padding: 12px 0 8px 0;
    font-size: 1rem;
    background: transparent;
    border: none;
    border-bottom: 2px solid var(--border);
    color: var(--text);
    transition: border-color 0.2s, box-shadow 0.2s;
    outline: none;
}

.form-group input:focus {
    border-bottom-color: var(--primary);
    box-shadow: 0 1px 0 0 var(--primary);
}

.form-group input::placeholder {
    color: var(--text-secondary);
    opacity: 0.6;
}

/* ===== 自建验证组件高仿极验 ===== */
.geetest-card {
    background: var(--surface);
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(0,0,0,0.12);
    padding: 20px 24px;
    min-width: 280px;
    border: 1px solid var(--border);
    transition: all 0.3s;
}

.geetest-card input {
    transition: border 0.2s;
}

.geetest-card .btn-primary {
    background: var(--primary);
    color: #fff;
}

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

.geetest-card .btn-primary:active {
    transform: scale(0.98);
}

/* ===== 标题/正文 ===== */
h1, h2, h3 {
    font-weight: 500;
    letter-spacing: -0.3px;
}
h1 { font-size: 2.2rem; }
h2 { font-size: 1.6rem; margin-bottom: 12px; }
h3 { font-size: 1.2rem; margin-bottom: 8px; }

/* ===== 代码块 ===== */
code, pre {
    background: var(--background);
    border-radius: 6px;
    font-family: "SF Mono", "Fira Code", monospace;
    font-size: 0.9rem;
}
pre {
    padding: 16px;
    overflow-x: auto;
    border: 1px solid var(--border);
    background: var(--surface);
}

/* ===== 页脚 ===== */
footer {
    margin-top: 40px;
    padding-top: 20px;
    border-top: 1px solid var(--border);
    text-align: center;
    color: var(--text-secondary);
    font-size: 0.85rem;
    width: 100%;
}

/* ===== 工具类 ===== */
.text-center { text-align: center; }
.mt-16 { margin-top: 16px; }
.mb-8 { margin-bottom: 8px; }
.flex { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; }

/* ===== Key 展示 ===== */
.key-display {
    display: flex;
    align-items: center;
    gap: 12px;
    flex-wrap: wrap;
    background: var(--background);
    padding: 8px 16px;
    border-radius: var(--radius);
    border: 1px solid var(--border);
}
.key-display code {
    font-size: 1.1rem;
    background: transparent;
    padding: 4px 0;
}

/* ===== 响应式微调 ===== */
@media (max-width: 600px) {
    .app-bar { flex-direction: column; align-items: stretch; }
    .app-bar nav { justify-content: center; }
    .card { padding: 16px; }
    .geetest-card { min-width: unset; padding: 16px; }
}