:root {
    --bg-initial-dark: #2c3e50;
    --bg-waiting-dark: #e67e22;
    --bg-go-dark: #27ae60;
    --text-dark: #ecf0f1;
    --shadow-dark: rgba(236, 240, 241, 0.5);
    --background-dark: #1c2833;
    --card-bg-dark: #2c3e50;
    --border-dark: #34495e;

    --bg-initial-light: #3498db;
    --bg-waiting-light: #f39c12;
    --bg-go-light: #2ecc71;
    --text-light: #2c3e50;
    --shadow-light: rgba(44, 62, 80, 0.3);
    --background-light: #ecf0f1;
    --card-bg-light: #ffffff;
    --border-light: #bdc3c7;

    --bg-initial: var(--bg-initial-dark);
    --bg-waiting: var(--bg-waiting-dark);
    --bg-go: var(--bg-go-dark);
    --text-color: var(--text-dark);
    --text-shadow-color: var(--shadow-dark);
    --background-color: var(--background-dark);
    --card-background: var(--card-bg-dark);
    --border-color: var(--border-dark);
    --header-footer-bg: var(--card-bg-dark);
}

body.light-mode {
    --bg-initial: var(--bg-initial-light);
    --bg-waiting: var(--bg-waiting-light);
    --bg-go: var(--bg-go-light);
    --text-color: var(--text-light);
    --text-shadow-color: var(--shadow-light);
    --background-color: var(--background-light);
    --card-background: var(--card-bg-light);
    --border-color: var(--border-light);
    --header-footer-bg: var(--card-bg-light);
}

html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    font-family: 'Inter', sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    line-height: 1.6;
}

/* --- Header --- */
.site-header {
    background-color: var(--header-footer-bg);
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 2rem;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1200px;
    margin: 0 auto;
}

.site-title {
    font-size: 1.5rem;
    font-weight: 700;
    margin: 0;
}

.main-nav a {
    margin: 0 1rem;
    text-decoration: none;
    color: var(--text-color);
    font-weight: 500;
}

.header-controls {
    display: flex;
    align-items: center;
    gap: 1rem;
}

#theme-toggle {
    background: none;
    border: 1px solid var(--border-color);
    color: var(--text-color);
    padding: 0.5rem 0.75rem;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.2s;
}

#theme-toggle:hover {
    background-color: var(--bg-initial);
}

/* Language Dropdown */
.language-dropdown {
    position: relative;
}

#language-selector-btn {
    background: none;
    border: 1px solid var(--border-color);
    color: var(--text-color);
    padding: 0.5rem 0.75rem;
    border-radius: 5px;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    transition: background-color 0.2s;
}

#language-selector-btn:hover {
    background-color: var(--bg-initial);
}

#language-selector-btn svg {
    transition: transform 0.2s;
}

.language-dropdown.open #language-selector-btn svg {
    transform: rotate(180deg);
}

#language-options {
    position: absolute;
    top: calc(100% + 5px);
    right: 0;
    background-color: var(--card-background);
    border: 1px solid var(--border-color);
    border-radius: 5px;
    box-shadow: 0 4px 8px rgba(0,0,0,0.1);
    display: flex;
    flex-direction: column;
    min-width: 120px;
    z-index: 1100;
}

#language-options a {
    padding: 0.75rem 1rem;
    text-decoration: none;
    color: var(--text-color);
    transition: background-color 0.2s;
}

#language-options a:hover {
    background-color: var(--bg-initial);
}

/* --- Main Content --- */
main {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem;
}

/* General utility */
.hidden { display: none !important; }

/* Test Container, Leaderboard, etc. remain the same */

#test-container {
    min-height: 70vh;
    display: flex;
    justify-content: center;
    align-items: center;
    cursor: pointer;
    border-radius: 10px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.2);
    transition: background-color 0.2s;
    background-image: url("data:image/svg+xml,%3Csvg width='40' height='40' viewBox='0 0 40 40' xmlns='http://www.w3.org/2000/svg'%3E%3Cg fill='%239C92AC' fill-opacity='0.1' fill-rule='evenodd'%3E%3Cpath d='M0 40L40 0H20L0 20M40 40V20L20 40'/%3E%3C/g%3E%3C/svg%3E");
}

.content {
    text-align: center;
}

#test-container h2 { font-size: 2.5rem; }
#instruction { font-size: 1.5rem; }
#result { font-size: 2rem; font-weight: bold;}

.initial { background-color: var(--bg-initial); }
.waiting { background-color: var(--bg-waiting); }
.go { background-color: var(--bg-go); }

.leaderboard-container {
    padding: 2rem;
    margin-top: 2rem;
    background-color: var(--card-background);
    border-radius: 10px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.2);
}

.leaderboard-container h2 {
    text-align: center;
    margin-top: 0;
}

#rank-table {
    width: 100%;
    border-collapse: collapse;
}

#rank-table th, #rank-table td {
    padding: 0.75rem 1rem;
    text-align: left;
    border-bottom: 1px solid var(--border-color);
}

.info-section {
    padding: 4rem 0;
}

.card {
    background-color: var(--card-background);
    border-radius: 10px;
    padding: 2rem;
    box-shadow: 0 4px 15px rgba(0,0,0,0.1);
}

.info-section h2 {
    border-bottom: 2px solid var(--bg-initial);
    padding-bottom: 0.5rem;
    margin-top: 0;
}

.site-footer {
    background-color: var(--header-footer-bg);
    border-top: 1px solid var(--border-color);
    padding: 2rem;
    text-align: center;
    color: #aaa;
    font-size: 0.9rem;
}

.site-footer nav a {
    margin: 0 1rem;
    color: #aaa;
    text-decoration: none;
}

#modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.7);
    display: none;
    justify-content: center;
    align-items: center;
    z-index: 2000;
}

#modal-content {
    width: 90%;
    max-width: 800px;
    max-height: 80vh;
    overflow-y: auto;
    position: relative;
}

#modal-close-btn {
    position: absolute;
    top: 10px;
    right: 20px;
    background: none;
    border: none;
    color: var(--text-color);
    font-size: 2rem;
    cursor: pointer;
    z-index: 2001;
}

@media (max-width: 768px) {
    .header-content {
        flex-direction: column;
        gap: 1rem;
    }
    .main-nav a {
        margin: 0 0.5rem;
    }
}