/* --- Color & Theme Variables (Neutral Theme) --- */
:root {
    --primary-accent: #007BFF;
    --success-green: #28A745;
    --danger-red: #DC3545;
    --warning-orange: #FFC107;
    --secondary-gray: #6C757D;
    --hint-purple: #6610f2;
    --bg-color: #F8F9FA;
    --container-bg: #FFFFFF;
    --text-color: #495057;
    --heading-color: #212529;
    --border-color: #DEE2E6;
    --light-gray: #F1F3F5;
    --shadow-color: rgba(0, 0, 0, 0.06);
}

[data-theme="dark"] {
    --bg-color: #121212;
    --container-bg: #1E1E1E;
    --text-color: #CED4DA;
    --heading-color: #E9ECEF;
    --border-color: #495057;
    --light-gray: #343A40;
    --shadow-color: rgba(0, 0, 0, 0.25);
}

/* --- General & Body Styling --- */
body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    padding-top: 80px;
    transition: background-color 0.3s, color 0.3s;
}

/* --- Top Navigation Bar --- */
.top-nav {
    background-color: var(--container-bg);
    border-bottom: 1px solid var(--border-color);
    box-shadow: 0 1px 3px var(--shadow-color);
    padding: 0 30px;
    position: fixed;
    top: 0;
    width: 100%;
    height: 60px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    z-index: 1000;
    box-sizing: border-box;
    transition: background-color 0.3s, border-bottom 0.3s;
}
.nav-brand h3 { margin: 0; color: var(--heading-color); }
.nav-links { display: flex; align-items: center; gap: 20px; }
.nav-links a:not(.dropdown-item) { text-decoration: none; color: var(--text-color); font-weight: 600; padding: 8px 12px; border-radius: 99px; transition: background-color 0.2s ease; cursor: pointer; }
.nav-links a:not(.dropdown-item):hover { background-color: var(--light-gray); }

/* --- Dark Mode Toggle (Slider Switch) --- */
.theme-switch { position: relative; display: inline-block; width: 60px; height: 34px; }
.theme-switch input { opacity: 0; width: 0; height: 0; }
.slider { position: absolute; cursor: pointer; top: 0; left: 0; right: 0; bottom: 0; background-color: #ccc; border-radius: 34px; transition: .4s; }
.slider:before { position: absolute; content: ""; height: 26px; width: 26px; left: 4px; bottom: 4px; background-color: white; border-radius: 50%; transition: .4s; }
input:checked + .slider { background-color: var(--primary-accent); }
input:checked + .slider:before { transform: translateX(26px); }

/* --- General Button Styling --- */
button { padding: 12px 24px; border: none; border-radius: 99px; font-size: 1em; font-weight: 600; cursor: pointer; transition: transform 0.2s ease, opacity 0.2s ease; color: white; }
button:hover { opacity: 0.9; transform: translateY(-2px); }

/* --- Color-Coded Buttons --- */
#check-button { background-color: var(--success-green); }
#new-problem-button { background-color: var(--warning-orange); color: #212529; }
#hint-button { background-color: var(--hint-purple); font-size: 0.9em; }
#login-button, #signup-button { background-color: var(--primary-accent); }
#logout-button { background-color: var(--danger-red); }

/* --- Layout & Main Containers --- */
.main-content { display: flex; flex-direction: column; align-items: center; gap: 30px; width: 100%; max-width: 550px; margin: 30px auto; padding: 0 20px; box-sizing: border-box; }
.container, .rules-container { background: var(--container-bg); padding: 30px; border-radius: 16px; border: 1px solid var(--border-color); box-shadow: 0 5px 25px var(--shadow-color); text-align: center; width: 100%; transition: background-color 0.3s, border 0.3s; }
h1, h2, h3 { color: var(--heading-color); margin-top: 0; }
.button-area { display: flex; justify-content: center; gap: 15px; margin: 25px 0; }

/* --- Settings, Game Area, Leaderboard --- */
.settings-area { display: flex; justify-content: center; gap: 20px; margin-bottom: 20px; flex-wrap: wrap; }
.setting-group { display: flex; align-items: center; gap: 10px; }
.setting-group label { font-weight: 600; }
.setting-group select { background-color: var(--container-bg); color: var(--text-color); border: 1px solid var(--border-color); border-radius: 6px; padding: 8px; font-size: 0.9em; }
.login-prompt { background-color: #fff3cd; color: #664d03; border: 1px solid #ffecb5; border-radius: 8px; padding: 15px; margin-bottom: 20px; }
.login-prompt a { font-weight: 600; color: var(--primary-accent); cursor: pointer; }
.problem h2 { font-size: 1.6em; color: var(--primary-accent); padding: 20px; background-color: var(--light-gray); border-radius: 8px; display: inline-block; margin: 20px 0; }
#answer-input { min-width: 280px; padding: 10px; border: 2px solid var(--border-color); border-radius: 8px; font-size: 1.3em; }
#feedback { margin-top: 20px; font-size: 1.1em; font-weight: bold; min-height: 25px; }
#feedback.correct { color: var(--success-green); }
#feedback.incorrect { color: var(--danger-red); }
#hint-text { background-color: rgba(255, 193, 7, 0.1); border: 1px solid rgba(255, 193, 7, 0.4); border-radius: 8px; padding: 15px; margin-top: 15px; color: var(--text-color); }
.rules-container ul { list-style: none; padding: 0; text-align: left; }
.rules-container li { padding: 12px 0; border-bottom: 1px solid var(--border-color); }
.rules-container li:last-child { border-bottom: none; }
#leaderboard-list li { display: flex; justify-content: space-between; font-size: 1.1em; }

/* --- Modals --- */
.modal-overlay { position: fixed; top: 0; left: 0; width: 100%; height: 100%; background-color: rgba(0, 0, 0, 0.5); display: grid; place-items: center; z-index: 2000; }
.modal-content { background: var(--container-bg); padding: 40px 30px 30px 30px; border-radius: 16px; width: 100%; max-width: 400px; position: relative; text-align: center; }
.modal-content input { width: 100%; box-sizing: border-box; padding: 12px 15px; margin-bottom: 15px; border: 1px solid var(--border-color); background-color: var(--light-gray); color: var(--text-color); border-radius: 8px; font-size: 1em; }
.modal-content button:not(.close-button) { width: 100%; }
.close-button { position: absolute; top: 10px; right: 15px; background: none; border: none; color: #aaa; font-size: 2em; font-weight: 600; line-height: 1; padding: 5px; cursor: pointer; transition: color 0.2s ease, transform 0.2s ease; }
.close-button:hover { color: var(--heading-color); transform: scale(1.1); }

/* --- Social Auth & Help Modal Styles --- */
.social-auth-container { display: flex; flex-direction: column; gap: 10px; margin-bottom: 20px; }
.social-btn { display: flex; align-items: center; justify-content: center; gap: 10px; width: 100%; padding: 10px; border: 1px solid var(--border-color); background-color: transparent; color: var(--text-color); transition: background-color 0.2s, border-color 0.2s; }
.social-btn:hover { background-color: var(--light-gray); }
.social-btn img { width: 20px; height: 20px; }
.divider { display: flex; align-items: center; text-align: center; color: #aaa; margin-bottom: 20px; }
.divider::before, .divider::after { content: ''; flex: 1; border-bottom: 1px solid var(--border-color); }
.divider:not(:empty)::before { margin-right: .5em; }
.divider:not(:empty)::after { margin-left: .5em; }
.github-btn img { filter: invert(1); }
[data-theme="dark"] .github-btn img { filter: none; }
.help-section { text-align: left; margin-bottom: 20px; }
.help-section h4 { margin-bottom: 8px; color: var(--primary-accent); }
.help-section p { margin: 5px 0; }

/* --- Footer & Privacy Page Styles --- */
footer { width: 100%; text-align: center; padding: 20px 0; margin-top: 20px; }
footer a { color: var(--secondary-gray); text-decoration: none; font-size: 0.9em; margin: 0 10px; }
.footer-separator { color: var(--secondary-gray); }
.privacy-content, .contact-container { text-align: left; }
.privacy-content h3 { margin-top: 25px; margin-bottom: 10px; color: var(--primary-accent); }
.back-link { display: inline-block; margin-top: 30px; font-weight: 600; color: var(--primary-accent); text-decoration: none; }
.contact-form { display: flex; flex-direction: column; gap: 15px; }
.form-group { display: flex; flex-direction: column; }
.form-group label { margin-bottom: 5px; font-weight: 600; }
.form-group input, .form-group textarea { padding: 10px; border-radius: 8px; border: 1px solid var(--border-color); background-color: var(--light-gray); color: var(--text-color); font-size: 1em; }

/* --- Dropdown Menu Styles --- */
.dropdown-container { position: relative; display: inline-block; }
.icon-button { background: none; border: none; cursor: pointer; font-size: 1.5em; padding: 0 8px; color: var(--text-color); border-radius: 8px; }
.icon-button:hover { background-color: var(--light-gray); }
#dropdown-menu { position: absolute; top: calc(100% + 10px); right: 0; background-color: var(--container-bg); border: 1px solid var(--border-color); border-radius: 12px; box-shadow: 0 8px 16px var(--shadow-color); z-index: 1100; width: 200px; padding: 8px; overflow: hidden; }
.dropdown-item { display: block; width: 100%; box-sizing: border-box; padding: 10px 15px; text-align: left; background: none; border: none; color: var(--text-color); font-size: 0.95em; font-weight: 500; text-decoration: none; border-radius: 8px; cursor: pointer; }
.dropdown-item:hover { background-color: var(--light-gray); color: var(--heading-color); }

/* --- Utility Class --- */
.hidden { display: none !important; }

/* --- Mobile Responsive Styles --- */
@media (max-width: 600px) {
    body { padding-top: 70px; }
    .main-content { padding: 0 15px; gap: 20px; }
    .container, .rules-container { padding: 20px; }
    .top-nav { padding: 0 15px; }
    h1 { font-size: 1.8em; }
    .problem h2 { font-size: 1.3em; padding: 15px; }
    .button-area { flex-direction: column; gap: 10px; }
    .settings-area { flex-direction: column; gap: 15px; }
    #answer-input { min-width: 0; width: 100%; }
    .modal-content { width: 90%; padding: 30px 20px 20px 20px; }
}