/* 全局基础样式 */
:root {
    --primary-color: #007bff;
    --secondary-color: #6c757d;
    --success-color: #28a745;
    --info-color: #17a2b8;
    --warning-color: #ffc107;
    --danger-color: #dc3545;
    --light-color: #f8f9fa;
    --dark-color: #343a40;
    --text-color: #333;
    --heading-color: #222;
    --background-color: #fff;
    --border-color: #dee2e6;
    --font-family-sans-serif: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji";
    --header-height: 70px;
    --top-bar-height: 40px;
}

/* Dark mode variables */
body.dark-mode {
    --primary-color: #66b3ff;
    --secondary-color: #99aab5;
    --background-color: #1a202c;
    --text-color: #e2e8f0;
    --heading-color: #f8f9fa;
    --border-color: #4a5568;
    --light-color: #2d3748;
    --dark-color: #e2e8f0;
}

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

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: var(--font-family-sans-serif);
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--background-color);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 15px;
}

a {
    color: var(--primary-color);
    text-decoration: none;
    transition: color 0.3s ease, text-decoration 0.3s ease;
}

a:hover {
    color: var(--primary-color);
    text-decoration: underline;
}

ul {
    list-style: none;
}

h1, h2, h3, h4, h5, h6 {
    color: var(--heading-color);
    line-height: 1.2;
    margin-bottom: 0.5em;
}

p {
    margin-bottom: 1em;
}

/* 按钮样式 */
.btn {
    display: inline-block;
    font-weight: 400;
    color: #fff;
    text-align: center;
    vertical-align: middle;
    user-select: none;
    background-color: var(--primary-color);
    border: 1px solid var(--primary-color);
    padding: 0.6rem 1.2rem;
    font-size: 1rem;
    line-height: 1.5;
    border-radius: 0.25rem;
    transition: color 0.15s ease-in-out, background-color 0.15s ease-in-out, border-color 0.15s ease-in-out, box-shadow 0.15s ease-in-out;
    cursor: pointer;
}

.btn:hover {
    background-color: #0056b3;
    border-color: #0056b3;
}

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

.btn-primary:hover {
    background-color: #0056b3;
    border-color: #0056b3;
}

.btn-secondary {
    color: var(--dark-color);
    background-color: var(--light-color);
    border-color: var(--light-color);
}

.btn-secondary:hover {
    color: var(--dark-color);
    background-color: #e2e6ea;
    border-color: #dae0e5;
}

.btn-subscribe {
    background-color: var(--success-color);
    border-color: var(--success-color);
    padding: 0.6rem 1rem;
    margin-left: 5px;
}

.btn-subscribe:hover {
    background-color: #218838;
    border-color: #1e7e34;
}

/* 表单元素 */
input[type="email"],
input[type="text"],
input[type="password"],
textarea,
select {
    display: block;
    width: 100%;
    padding: 0.75rem 1rem;
    font-size: 1rem;
    line-height: 1.5;
    color: var(--text-color);
    background-color: var(--background-color);
    background-clip: padding-box;
    border: 1px solid var(--border-color);
    border-radius: 0.25rem;
    transition: border-color 0.15s ease-in-out, box-shadow 0.15s ease-in-out;
}

input[type="email"]:focus,
input[type="text"]:focus,
input[type="password"]:focus,
textarea:focus,
select:focus {
    color: var(--text-color);
    background-color: var(--background-color);
    border-color: var(--primary-color);
    outline: 0;
    box-shadow: 0 0 0 0.2rem rgba(0, 123, 255, 0.25);
}

/* 布局辅助 */
.flex-center {
    display: flex;
    align-items: center;
    justify-content: center;
}

.flex-between {
    display: flex;
    align-items: center;
    justify-content: space-between;
}

/* 响应式基础 */
@media (max-width: 768px) {
    .container {
        padding: 0 10px;
    }
    h1 { font-size: 2em; }
    h2 { font-size: 1.75em; }
}

/* Dark mode specific styles */
body.dark-mode .btn-secondary {
    color: var(--light-color);
    background-color: var(--dark-color);
    border-color: var(--dark-color);
}
body.dark-mode .btn-secondary:hover {
    color: var(--light-color);
    background-color: #4a5568;
    border-color: #4a5568;
}
body.dark-mode input, body.dark-mode select, body.dark-mode textarea {
    background-color: var(--light-color);
    border-color: var(--border-color);
    color: var(--text-color);
}
body.dark-mode input:focus, body.dark-mode select:focus, body.dark-mode textarea:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 0.2rem rgba(102, 179, 255, 0.25);
}

/* 辅助类，确保页脚始终在底部 */
body {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}
#page-content-wrapper {
    flex: 1;
}

/* Back to Top Button */
#backToTopBtn {
    display: none; /* Hidden by default */
    position: fixed; /* Fixed/sticky position */
    bottom: 30px; /* Place the button at the bottom of the page */
    right: 30px; /* Place the button 30px from the right */
    z-index: 99; /* Make sure it does not overlap */
    border: none; /* Remove borders */
    outline: none; /* Remove outline */
    background-color: var(--primary-color); /* Set a background color */
    color: white; /* Text color */
    cursor: pointer; /* Add a mouse pointer on hover */
    padding: 15px; /* Some padding */
    border-radius: 50%; /* Rounded corners */
    font-size: 18px; /* Increase font size */
    box-shadow: 0 2px 5px rgba(0,0,0,0.2);
    transition: background-color 0.3s ease, transform 0.3s ease;
}

#backToTopBtn:hover {
    background-color: #0056b3; /* Darker background on hover */
    transform: translateY(-2px);
}
/* 移动端内容区防溢出（系统追加，请勿删除） */
@media (max-width: 768px) {
  .page-content img {
    max-width: 100% !important;
    height: auto !important;
    display: block;
  }
  .page-content {
    overflow-x: hidden;
    max-width: 100%;
  }
  body {
    overflow-x: hidden;
  }
}