:root {
    /* Light Mode Variables */
    --bg-color-light: #f4f7f9;
    --text-color-light: #333;
    --heading-color-light: #111;
    --primary-color-light: #007aff;
    --accent-color-light: #FF9500;
    --component-bg-light: #ffffff;
    --border-color-light: #e1e4e8;

    /* Dark Mode Variables */
    --bg-color-dark: #121212;
    --text-color-dark: #e0e0e0;
    --heading-color-dark: #ffffff;
    --primary-color-dark: #0a84ff;
    --accent-color-dark: #ff9f0a;
    --component-bg-dark: #1e1e1e;
    --border-color-dark: #333;
}

body {
    font-family: 'Noto Sans KR', sans-serif;
    margin: 0;
    padding: 0;
    background-color: var(--bg-color, var(--bg-color-light));
    color: var(--text-color, var(--text-color-light));
    line-height: 1.6;
    transition: background-color 0.3s, color 0.3s;
}

body.dark-mode {
    --bg-color: var(--bg-color-dark);
    --text-color: var(--text-color-dark);
    --heading-color: var(--heading-color-dark);
    --primary-color: var(--primary-color-dark);
    --accent-color: var(--accent-color-dark);
    --component-bg: var(--component-bg-dark);
    --border-color: var(--border-color-dark);
}

.container {
    max-width: 900px;
    margin: 0 auto;
    padding: 20px;
}

/* --- Header --- */
.site-header {
    background-color: var(--component-bg, var(--component-bg-light));
    border-bottom: 1px solid var(--border-color, var(--border-color-light));
    padding: 10px 0;
    position: sticky;
    top: 0;
    z-index: 100;
    transition: background-color 0.3s, border-color 0.3s;
}

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

.logo a {
    font-size: 1.5em;
    font-weight: 700;
    color: var(--heading-color, var(--heading-color-light));
    text-decoration: none;
}

.main-nav ul {
    margin: 0;
    padding: 0;
    list-style: none;
    display: flex;
}

.main-nav li {
    margin-left: 20px;
}

.main-nav a {
    text-decoration: none;
    color: var(--text-color, var(--text-color-light));
    font-weight: 500;
    transition: color 0.2s;
}

.main-nav a:hover {
    color: var(--primary-color, var(--primary-color-light));
}

/* --- Main Content --- */
main {
    padding: 40px 0;
}

.hero {
    text-align: center;
    margin-bottom: 60px;
}

.hero h2 {
    font-size: 2.5em;
    color: var(--heading-color, var(--heading-color-light));
    margin-bottom: 10px;
}

focus-timer {
    display: block;
    margin: 40px auto;
}

.content-section {
    background-color: var(--component-bg, var(--component-bg-light));
    padding: 30px;
    border-radius: 8px;
    margin-bottom: 30px;
    border: 1px solid var(--border-color, var(--border-color-light));
}

.content-section h3, .page-title h2 {
    font-size: 1.8em;
    color: var(--heading-color, var(--heading-color-light));
    border-bottom: 2px solid var(--primary-color, var(--primary-color-light));
    padding-bottom: 10px;
    margin-top: 0;
}

.page-title {
    text-align: center;
    background: none;
    border: none;
}

.content-section ul, .content-section ol {
    padding-left: 20px;
}

/* --- Contact Form --- */
.contact-form .form-group {
    margin-bottom: 20px;
}

.contact-form label {
    display: block;
    margin-bottom: 5px;
    font-weight: bold;
}

.contact-form input[type="text"],
.contact-form input[type="email"],
.contact-form textarea {
    width: 100%;
    padding: 10px;
    border: 1px solid var(--border-color, var(--border-color-light));
    border-radius: 5px;
    background-color: var(--bg-color, var(--bg-color-light));
    color: var(--text-color, var(--text-color-light));
}

.btn-submit {
    display: inline-block;
    background-color: var(--primary-color, var(--primary-color-light));
    color: white;
    padding: 12px 25px;
    border: none;
    border-radius: 5px;
    font-size: 1em;
    cursor: pointer;
    transition: background-color 0.2s;
}

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


/* --- Footer --- */
.site-footer {
    text-align: center;
    padding: 20px 0;
    margin-top: 40px;
    background-color: var(--component-bg, var(--component-bg-light));
    border-top: 1px solid var(--border-color, var(--border-color-light));
    font-size: 0.9em;
}

.footer-nav ul {
    margin: 10px 0 0;
    padding: 0;
    list-style: none;
    display: flex;
    justify-content: center;
}

.footer-nav li {
    margin: 0 10px;
}

.footer-nav a {
    color: var(--text-color, var(--text-color-light));
    text-decoration: none;
}

.footer-nav a:hover {
    text-decoration: underline;
}