/* Google Fonts */
@import url('https://fonts.googleapis.com/css2?family=Black+Han+Sans&family=Do+Hyeon&family=Dokdo&family=Dongle:wght@300;400;700&family=Gaegu:wght@300;400;700&family=Gamja+Flower&family=Gothic+A1:wght@400;700&family=Gowun+Batang&family=Gowun+Dodum&family=Hahmlet:wght@400;700&family=Hi+Melody&family=Jua&family=Kirang+Haerang&family=Nanum+Brush+Script&family=Nanum+Gothic:wght@400;700&family=Nanum+Myeongjo:wght@400;700&family=Nanum+Pen+Script&family=Noto+Sans+KR:wght@300;400;500;700&family=Noto+Serif+KR:wght@200;300;400;500;600;700;900&family=Poor+Story&family=Single+Day&family=Song+Myung&family=Stylish&family=Sunflower:wght@300;500;700&family=Yeon+Sung&display=swap');

:root {
    /* Achromatic / Clean Blue Theme */
    --bg-app: #FFFFFF;
    /* Pure White App Background (or very light gray) */
    --bg-surface: #FFFFFF;
    --text-main: #212529;
    --text-sub: #868E96;
    --border: #E9ECEF;
    --border-hover: #CED4DA;

    --primary: #212529;
    /* Black for Primary Actions (Modes) */
    --primary-text: #FFFFFF;

    --accent-blue: #339AF0;
    /* For Links / Highlights */
    --accent-blue-soft: #D0EBFF;

    --bg-card: #FFFFFF;
    /* If body is gray, card is white. Let's make body white too or soft gray? */
    /* Samuel style: Body white, or soft gray with white card? 
       Let's go for Body #F8F9FA, Card #FFFFFF */
    --bg-body: #F9FAFB;

    --success: #2B8A3E;
    --fail: #C92A2A;
    --warning: #F39C12;

    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 8px 30px rgba(0, 0, 0, 0.12);

    --modal-overlay: rgba(0, 0, 0, 0.4);
    --app-font: 'Noto Sans KR', 'Malgun Gothic', sans-serif;

    --btn-primary-bg: #339AF0;
    --btn-primary-text: #FFFFFF;
}

[data-theme="dark"] {
    --bg-body: #121212;
    --bg-card: #1E1E1E;
    --bg-app: #121212;
    --bg-surface: #1E1E1E;

    --text-main: #E0E0E0;
    --text-sub: #A0A0A0;

    --border: #333333;
    --border-hover: #495057;

    --primary: #E0E0E0;
    /* High contrast mode buttons in dark */
    --primary-text: #121212;

    --accent-blue: #339AF0;
    --accent-blue-soft: #182A3A;

    --success: #69DB7C;
    --fail: #FF8787;
    --warning: #FCC419;

    --shadow-sm: none;
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.5);
    --shadow-lg: 0 8px 30px rgba(0, 0, 0, 0.5);

    --btn-primary-bg: #339AF0;
    --btn-primary-text: #FFFFFF;
}

[data-theme="dark"] .btn-icon,
[data-theme="dark"] .btn-icon-text {
    color: #FFFFFF;
    border-color: #555;
}

[data-theme="dark"] .btn-icon:hover,
[data-theme="dark"] .btn-icon-text:hover {
    border-color: #FFFFFF;
}

[data-theme="dark"] .btn-mode:hover {
    color: #FFFFFF;
}

[data-theme="dark"] .btn-mode.active {
    background: #FFFFFF;
    color: #000000;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: var(--app-font);
    outline: none;
}

body {
    background-color: var(--bg-body);
    color: var(--text-main);
    height: 100vh;
    /* Fallback */
    height: 100dvh;
    /* Mobile friendly */
    overflow: hidden;
    font-weight: 700;
    /* App-like feel */
}

/* ========================================
   App Layout
   ======================================== */
.app-layout {
    display: flex;
    flex-direction: column;
    height: 100%;
    max-width: 1600px;
    margin: 0 auto;
    padding: 0 20px;
    position: relative;
}

/* ========================================
   1. Top Nav
   ======================================== */
.top-nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 0;
    border-bottom: 1px solid var(--border);
    margin-bottom: 20px;
    flex-shrink: 0;
}

.nav-left {
    display: flex;
    align-items: center;
    gap: 12px;
}

.nav-right {
    display: flex;
    flex-direction: column;
    align-items: flex-end;
    gap: 4px;
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: 4px;
}

.font-controls {
    display: flex;
    gap: 8px;
}

/* Dropdowns */
.nav-select {
    background: transparent;
    border: none;
    font-size: 0.95rem;
    font-weight: 700;
    color: var(--text-main);
    cursor: pointer;
    padding: 4px 8px;
    border-radius: 4px;
    transition: background 0.2s;
}

select option {
    background-color: var(--bg-surface);
    color: var(--text-main);
}


.nav-select:hover {
    background-color: rgba(0, 0, 0, 0.04);
}

.divider {
    color: var(--border);
    font-size: 0.8rem;
    margin: 0 4px;
}

/* Custom Hover Dropdown */
.dropdown {
    position: relative;
    display: inline-block;
}

.dropbtn {
    background: transparent;
    border: none;
    font-size: 0.95rem;
    font-weight: 700;
    color: var(--text-main);
    cursor: pointer;
    padding: 8px 12px;
    border-radius: 4px;
    transition: background 0.2s;
    display: flex;
    align-items: center;
    gap: 4px;
}

.dropbtn:hover {
    background-color: rgba(0, 0, 0, 0.04);
}

[data-theme="dark"] .dropbtn:hover {
    background-color: rgba(255, 255, 255, 0.1);
}

.dropdown-content {
    display: none;
    position: absolute;
    background-color: var(--bg-surface);
    min-width: 120px;
    box-shadow: var(--shadow-md);
    border-radius: 8px;
    z-index: 1000;
    border: 1px solid var(--border);
    top: 100%;
    left: 0;
    overflow: hidden;
}

.dropdown:hover .dropdown-content {
    display: block;
}

.dropdown-item {
    color: var(--text-main);
    padding: 10px 16px;
    text-decoration: none;
    display: block;
    cursor: pointer;
    font-size: 0.9rem;
    transition: background 0.2s;
    white-space: pre;
}

.dropdown-item:hover {
    background-color: var(--bg-body);
}

[data-theme="dark"] .dropdown-item:hover {
    background-color: #3E3E3E;
}

.dropdown-item.active {
    background-color: var(--accent-blue-soft);
    color: var(--accent-blue);
    font-weight: bold;
}

[data-theme="dark"] .dropdown-item.active {
    background-color: #183C5C;
    color: #4DABF7;
}

/* Buttons in Header */
.btn-pill {
    background: var(--bg-surface);
    border: 1px solid var(--border);
    color: var(--text-main);
    padding: 8px 20px;
    border-radius: 20px;
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    display: flex;
    align-items: center;
    gap: 6px;
    box-shadow: var(--shadow-sm);
}

.btn-pill:hover {
    border-color: var(--border-hover);
    transform: translateY(-1px);
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.08);
    font-weight: 700;
}

.btn-pill.delete {
    color: var(--fail);
}

.btn-pill.delete:hover {
    border-color: var(--fail);
    background: #FFF5F5;
}

.btn-icon {
    background: transparent;
    border: 1px solid var(--border);
    width: 40px;
    height: 40px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: 1rem;
    transition: all 0.2s;
    color: #000000;
    font-weight: 700;
}

.btn-icon:hover {
    color: #000000;
    border-color: #000000;
    background: #FFFFFF;
}

.btn-icon-text {
    background: transparent;
    border: 1px solid var(--border);
    height: 40px;
    padding: 0 12px;
    border-radius: 20px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: 0.95rem;
    transition: all 0.2s;
    color: #000000;
    font-weight: 700;
    white-space: nowrap;
}

.btn-icon-text:hover {
    color: #000000;
    border-color: #000000;
    background: #FFFFFF;
}

/* ========================================
   2. Mode Bar (Centered Pill)
   ======================================== */
.mode-bar {
    display: flex;
    justify-content: center;
    align-items: center;
    position: relative;
    padding: 10px 0 30px 0;
    flex-shrink: 0;
}

.mode-group {
    background: #F1F3F5;
    padding: 4px;
    border-radius: 30px;
    display: flex;
    gap: 4px;
}

[data-theme="dark"] .mode-group {
    background: var(--border);
}

.mode-item-group {
    display: flex;
    align-items: center;
    gap: 2px;
}

/* .btn-settings styles removed */

.btn-mode {
    background: transparent;
    border: none;
    padding: 10px 24px;
    border-radius: 24px;
    font-size: 1rem;
    color: var(--text-sub);
    font-weight: 700;
    cursor: pointer;
    transition: all 0.2s;
}

.btn-mode:hover {
    color: #000000;
}

.btn-mode.active {
    background: #000000;
    /* Black */
    color: white;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.2);
}

/* .help-btn removed */

.btn-text {
    background: transparent;
    border: none;
    color: var(--text-sub);
    font-size: 1rem;
    cursor: pointer;
    font-weight: 500;
}

.btn-text:hover {
    color: var(--text-main);
    text-decoration: underline;
}

#btnTTS.active {
    color: var(--accent-blue);
    font-weight: 700;
}

.voice-select {
    padding: 4px;
    margin-right: 8px;
    border: 1px solid var(--border);
    border-radius: 4px;
    background: var(--bg-surface);
    color: var(--text-main);
    font-size: 0.8rem;
    max-width: 120px;
}

.btn-icon-small {
    background: none;
    border: none;
    cursor: pointer;
    font-size: 1.4rem;
    margin-right: 8px;
    padding: 0;
    vertical-align: middle;
}

.help-text {
    text-align: left;
    font-size: 0.95rem;
    line-height: 1.6;
    margin-bottom: 20px;
    color: var(--text-main);
}

.help-text ol {
    padding-left: 24px;
    margin-top: 5px;
    margin-bottom: 10px;
}

.help-text hr {
    margin: 15px 0;
    border: 0;
    border-top: 1px solid var(--border);
}

/* ========================================

/* ========================================
   3. Main Content (Card)
   ======================================== */
.main-container {
    flex-grow: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    /* justify-content: center; Removed to prevent clipping when content overflows */
    gap: 30px;
    padding-bottom: 40px;
    overflow-y: auto;
}

.problem-card {
    background: var(--bg-card);
    width: 100%;
    max-width: 1100px;
    min-height: 400px;
    height: auto;
    flex-shrink: 0;
    /* Allow growth */
    border-radius: 24px;
    box-shadow: var(--shadow-sm);
    padding: 60px 40px 40px 40px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    text-align: center;
    font-size: 1.8rem;
    line-height: 1.8;
    word-break: break-word;
    overflow-wrap: break-word;
    border: 1px solid var(--border);
    transition: box-shadow 0.3s;
    margin: 40px auto;
    font-size: var(--app-font-size, 24px);
}

@media (max-width: 768px) {
    .problem-card {
        /* Cap the font size on mobile to prevent overflow */
        /* Use min() to take the smaller of the user setting or the cap */
        font-size: min(var(--app-font-size, 24px), 22px) !important;
    }
}

/* Reference Block (Dynamic from JS) */
.reference-block {
    display: block;
    margin-bottom: 30px;
    font-weight: 700;
    font-size: 1.2em;
    color: var(--text-main);
}

/* Verse Text Content (Dynamic from JS) */
.verse-content {
    display: block;
    width: 100%;
    text-align: center;
    /* text-align: left; Removed based on user feedback */
    line-height: 2.0;
    /* Switching to LEFT to prevent jumping */
    line-height: 2.0;
    /* relaxed reading */
}

.problem-card:hover {
    box-shadow: var(--shadow-md);
}

.placeholder {
    color: var(--text-sub);
    font-size: 1.2rem;
}

/* Input */
.input-container {
    width: 100%;
    max-width: 600px;
}

#answerInput {
    width: 100%;
    border: none;
    border-bottom: 2px solid var(--border);
    background: transparent;
    padding: 15px 0;
    font-size: 1.2rem;
    text-align: center;
    color: var(--text-main);
    transition: border-color 0.3s;
}

#answerInput:focus {
    border-color: var(--text-main);
    /* Active black underline */
}

#answerInput::placeholder {
    color: #ADB5BD;
    font-weight: 300;
}

/* ========================================
   4. Bottom Bar
   ======================================== */
.bottom-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 0;
    border-top: 1px solid var(--border);
    /* Or minimal border */
    flex-shrink: 0;
}

.status-left {
    color: var(--text-sub);
    font-size: 0.9rem;
    font-weight: 500;
}

.actions-right {
    display: flex;
    gap: 20px;
}

.btn-text.danger {
    color: var(--fail);
}

.btn-text.danger:hover {
    color: #A61E4D;
}

/* ========================================
   5. Modals (Preserved & Cleaned)
   ======================================== */
.modal {
    display: none;
    position: fixed;
    z-index: 2000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background-color: var(--modal-overlay);
    backdrop-filter: blur(4px);
    /* Modern blur */
    align-items: center;
    justify-content: center;
}

.modal-content {
    background-color: var(--bg-card);
    margin: 0;
    padding: 40px;
    width: 90%;
    max-width: 450px;
    border-radius: 16px;
    box-shadow: var(--shadow-lg);
    position: relative;
    display: flex;
    flex-direction: column;
    gap: 20px;
    border: none;
}

.modal-content h2 {
    font-size: 1.4rem;
    color: var(--text-main);
    text-align: center;
    margin-bottom: 10px;
}

.close {
    position: absolute;
    top: 20px;
    right: 20px;
    font-size: 1.5rem;
    color: var(--text-sub);
    cursor: pointer;
}

/* Modal Inputs */
.easy-input-container {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.input-group label {
    display: block;
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-main);
    margin-bottom: 8px;
}

.input-group input,
.input-group select,
.input-group textarea {
    width: 100%;
    padding: 14px;
    border: 1px solid var(--border);
    border-radius: 12px;
    font-size: 1rem;
    background: var(--bg-body);
    transition: all 0.2s;
    outline: none;
    color: var(--text-main);
}

[data-theme="dark"] .input-group input,
[data-theme="dark"] .input-group select,
[data-theme="dark"] .input-group textarea {
    background: #2C2C2C;
    /* Slightly lighter than card #1E1E1E */
    border-color: #444;
}

[data-theme="dark"] .input-group input::placeholder,
[data-theme="dark"] .input-group textarea::placeholder {
    color: #888;
}

[data-theme="dark"] .input-group input:focus,
[data-theme="dark"] .input-group select:focus,
[data-theme="dark"] .input-group textarea:focus {
    background: #3E3E3E;
    border-color: #FFFFFF;
}

.input-group textarea {
    resize: vertical;
    min-height: 100px;
    line-height: 1.5;
}

.input-group input:focus,
.input-group select:focus,
.input-group textarea:focus {
    background: #FFFFFF;
    border-color: var(--text-main);
    box-shadow: 0 0 0 2px rgba(33, 37, 41, 0.1);
}

/* Row styles removed as we switched to vertical stack */

.modal-actions {
    display: flex;
    justify-content: flex-end;
    gap: 10px;
    margin-top: 10px;
}

.btn-save,
.btn-add {
    background: var(--btn-primary-bg);
    color: var(--btn-primary-text);
    border: none;
    padding: 12px 28px;
    border-radius: 8px;
    font-weight: 600;
    cursor: pointer;
}

.btn-save:hover,
.btn-add:hover {
    filter: brightness(1.1);
}

.btn-save:hover {
    background: #000;
}

/* Verse List */
.verse-list-container {
    max-height: 250px;
    overflow-y: auto;
    border: 1px solid var(--border);
    border-radius: 8px;
}

.verse-item {
    background: var(--bg-surface);
    padding: 12px;
    border-bottom: 1px solid var(--border);
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 10px;
}

[data-theme="dark"] .verse-item {
    background: #2C2C2C;
    border-color: #444;
}

.verse-info {
    display: flex;
    flex-direction: column;
    gap: 2px;
    flex: 1;
    overflow: hidden;
}

.verse-text {
    font-size: 0.9rem;
    color: var(--text-main);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.btn-delete-item {
    background-color: var(--fail);
    color: white;
    border: none;
    padding: 8px 14px;
    border-radius: 8px;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    flex-shrink: 0;
    transition: filter 0.2s;
}

.btn-delete-item:hover {
    filter: brightness(0.9);
}

.verse-level {
    color: var(--accent-blue);
    font-weight: bold;
    margin-right: 6px;
}

/* ========================================
   6. Utilities / States
   ======================================== */
.correct {
    color: var(--success);
    font-weight: bold;
}

.wrong {
    color: var(--fail);
    font-weight: bold;
}

.hint-text {
    color: var(--warning);
    font-weight: bold;
}

/* Control Groups in Footer */
.actions-right {
    display: flex;
    gap: 15px;
    align-items: center;
}

.control-group {
    display: flex;
    gap: 8px;
    align-items: center;
    padding: 4px 8px;
    border-radius: 8px;
}

.audio-controls {
    background-color: rgba(0, 0, 0, 0.03);
    /* Subtle background */
    border: 1px solid rgba(0, 0, 0, 0.05);
}

[data-theme="dark"] .audio-controls {
    background-color: rgba(255, 255, 255, 0.05);
    border: 1px solid rgba(255, 255, 255, 0.1);
}

.game-controls {
    padding-left: 12px;
    border-left: 1px solid var(--border);
    display: flex;
    gap: 15px;
}

@keyframes shake {

    0%,
    100% {
        transform: translateX(0);
    }

    10%,
    30%,
    50%,
    70%,
    90% {
        transform: translateX(-4px);
    }

    20%,
    40%,
    60%,
    80% {
        transform: translateX(4px);
    }
}

.shake {
    animation: shake 0.4s cubic-bezier(.36, .07, .19, .97) both;
}

/* Custom Scrollbar */
::-webkit-scrollbar {
    width: 8px;
}

::-webkit-scrollbar-track {
    background: transparent;
}

::-webkit-scrollbar-thumb {
    background: #DEE2E6;
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: #ADB5BD;
}

/* Font Settings Modal */
.font-modal-content {
    max-width: 500px;
}

/* ========================================
   7. Background Themes
   ======================================== */

/* Theme Grid in Modal */
.theme-grid-container h3 {
    margin: 15px 0 10px 0;
    font-size: 1rem;
    color: var(--text-sub);
}

.theme-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(60px, 1fr));
    gap: 10px;
}

.theme-option {
    width: 60px;
    height: 60px;
    border-radius: 50%;
    border: 2px solid transparent;
    cursor: pointer;
    box-shadow: var(--shadow-sm);
    transition: transform 0.2s, border-color 0.2s;
}

.theme-option:hover {
    transform: scale(1.05);
}

.theme-option.active {
    border-color: var(--text-main);
    transform: scale(1.1);
}

/* --- Theme Classes (Applied to Body) --- */

/* Simple (Default handled by :root variables, just ensuring clean slate) */
.bg-simple {
    background-color: var(--bg-body);
    background-image: none;
}

/* Gradients */
/* Solid Colors */
.bg-solid-white {
    background-color: #F8F9FA;
    background-image: none;
}

.bg-solid-cream {
    background-color: #FDFBF7;
    background-image: none;
}

.bg-solid-paper {
    background-color: #F4ECD8;
    background-image: none;
}

/* Dark Colors */
.bg-solid-dark-gray {
    background-color: #343A40;
    background-image: none;
}

.bg-solid-black {
    background-color: #121212;
    background-image: none;
}

.bg-solid-navy {
    background-color: #0F172A;
    /* Slate 900 */
    background-image: none;
}

.bg-solid-forest {
    background-color: #143601;
    background-image: none;
}

/* Glassmorphism for Panels */
.glass-mode .app-container {
    background: transparent;
}

.glass-mode .top-bar,
.glass-mode .bottom-bar,
.glass-mode .mode-bar,
.glass-mode .problem-card {
    background: rgba(255, 255, 255, 0.7);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.3);
}

.glass-mode .btn-mode {
    background: rgba(255, 255, 255, 0.6);
}

.glass-mode .btn-mode.active {
    background: rgba(255, 255, 255, 0.95);
    color: #212529;
    /* Enforce dark text */
    font-weight: bold;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

[data-theme="dark"].glass-mode .top-bar,
[data-theme="dark"].glass-mode .bottom-bar,
[data-theme="dark"].glass-mode .mode-bar,
[data-theme="dark"].glass-mode .problem-card {
    background: rgba(30, 30, 30, 0.7);
    border: 1px solid rgba(255, 255, 255, 0.05);
}

[data-theme="dark"].glass-mode .btn-mode {
    background: rgba(255, 255, 255, 0.1);
}

[data-theme="dark"].glass-mode .btn-mode.active {
    background: rgba(255, 255, 255, 0.9);
    color: #121212;
    /* Enforce dark text on white glass */
    font-weight: bold;
}

.font-settings-container {
    display: flex;
    flex-direction: column;
    gap: 15px;
}

.font-list-container {
    border: 1px solid var(--border);
    border-radius: 8px;
    height: 200px;
    overflow-y: auto;
    padding: 10px;
    background: #F8F9FA;
}

[data-theme="dark"] .font-list-container {
    background: #2C2C2C;
    border-color: #444;
}

.font-item {
    padding: 10px;
    border-bottom: 1px solid var(--border);
    cursor: pointer;
    border-radius: 4px;
    transition: background 0.2s;
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.1rem;
}

[data-theme="dark"] .font-item {
    border-bottom-color: #444;
    color: #E0E0E0;
}

.font-item:hover {
    background: #E9ECEF;
}

[data-theme="dark"] .font-item:hover {
    background: #3E3E3E;
}

.font-item.active {
    background: var(--accent-blue-soft);
    font-weight: bold;
    color: var(--accent-blue);
}

[data-theme="dark"] .font-item.active {
    background: #183C5C;
    /* Darker blue background */
    color: #4DABF7;
    /* Lighter blue text */
}

.font-controls-area {
    display: flex;
    flex-direction: column;
    gap: 15px;
    padding: 10px 0;
    border-top: 1px solid var(--border);
    border-bottom: 1px solid var(--border);
}

.control-row {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 15px;
}

input[type=range] {
    flex-grow: 1;
    accent-color: var(--text-main);
}

/* Checkbox Style */
.checkbox-label {
    display: flex;
    align-items: center;
    cursor: pointer;
    font-size: 1rem;
    gap: 10px;
}

.checkbox-label input {
    position: absolute;
    opacity: 0;
    cursor: pointer;
    height: 0;
    width: 0;
}

.checkmark {
    height: 20px;
    width: 20px;
    background-color: #EEE;
    border-radius: 4px;
    position: relative;
    border: 1px solid var(--border);
}

.checkbox-label:hover input~.checkmark {
    background-color: #CCC;
}

.checkbox-label input:checked~.checkmark {
    background-color: var(--text-main);
}

.checkmark:after {
    content: "";
    position: absolute;
    display: none;
}

.checkbox-label input:checked~.checkmark:after {
    display: block;
}

.checkbox-label .checkmark:after {
    left: 6px;
    top: 2px;
    width: 5px;
    height: 10px;
    border: solid white;
    border-width: 0 3px 3px 0;
    transform: rotate(45deg);
}

/* Settings Modal */
.setting-modal-content {
    max-width: 400px;
    text-align: center;
}

.setting-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    margin-top: 20px;
}

.btn-option {
    padding: 10px;
    border: 1px solid var(--border);
    border-radius: 8px;
    background: var(--bg-surface);
    color: var(--text-main);
    cursor: pointer;
    transition: all 0.2s;
    font-size: 0.9rem;
}

.btn-option:hover {
    border-color: var(--accent-blue);
    background: var(--bg-body);
}

.btn-option.active {
    background: var(--accent-blue);
    color: #FFF;
    border-color: var(--accent-blue);
}

/* ========================================
   7. Responsive Design (Adaptive UI)
   ======================================== */

/* Table & Small Desktop (Max 1024px) */
@media (max-width: 1024px) {
    .app-layout {
        padding: 0 16px;
    }

    .top-nav {
        flex-direction: column;
        gap: 15px;
        align-items: stretch;
        padding: 15px 0;
    }

    .nav-left,
    .nav-right {
        justify-content: space-between;
        width: 100%;
    }

    .main-container {
        gap: 20px;
        padding-bottom: 20px;
    }

    .problem-card {
        padding: 40px 30px;
        min-height: 300px;
        width: 100%;
        margin: 20px 0;
    }
}

/* Mobile Devices (Max 768px) */
@media (max-width: 768px) {
    :root {
        --font-size-base: 14px;
    }

    .app-layout {
        padding: 0 10px;
    }

    .top-nav {
        flex-direction: column;
        gap: 10px;
        /* Reduced gap */
        align-items: stretch;
        padding: 10px 0;
    }

    .nav-left {
        flex-direction: row;
        justify-content: space-between;
        width: 100%;
    }

    .nav-right {
        flex-direction: row;
        justify-content: space-between;
        width: 100%;
    }

    .font-controls {
        flex-wrap: wrap;
        /* Allow wrapping */
        justify-content: center;
        gap: 4px;
        /* Smaller gap */
    }

    .select-group {
        flex-wrap: wrap;
        gap: 4px;
    }

    .dropbtn {
        padding: 6px 8px;
        /* Smaller padding for dropbtn */
        font-size: 0.85rem;
    }

    .problem-card {
        margin: 10px auto;
        padding: 30px 15px;
        /* Cap the font size on mobile to prevent overflow */
        font-size: min(var(--app-font-size, 24px), 22px) !important;
        min-height: 30vh;
    }

    .mode-bar {
        padding: 5px 0 10px 0;
        width: 100%;
    }

    .mode-group {
        width: 100%;
        overflow-x: auto;
        -webkit-overflow-scrolling: touch;
        /* Smooth scrolling */
        scrollbar-width: none;
        /* Firefox */
    }

    .mode-group::-webkit-scrollbar {
        display: none;
        /* Chrome/Safari */
    }

    .mode-grid {
        display: flex;
        flex-wrap: nowrap;
        gap: 4px;
    }

    .btn-mode {
        padding: 8px 14px;
        font-size: 0.85rem;
        white-space: nowrap;
        flex: 0 0 auto;
        /* Prevent shrinking */
    }

    .bottom-bar {
        flex-direction: column;
        gap: 10px;
        padding: 10px 0 20px 0;
    }

    .actions-right {
        flex-direction: column;
        /* Stack controls on mobile */
        width: 100%;
        gap: 10px;
    }

    .audio-controls,
    .game-controls {
        display: flex;
        justify-content: center;
        flex-wrap: wrap;
        gap: 10px;
        width: 100%;
    }

    /* Adjust Modal for Mobile */
    .modal-content {
        width: 95%;
        margin: 5vh auto;
        padding: 20px;
    }

    .setting-grid {
        grid-template-columns: repeat(3, 1fr);
        /* 3 columns on mobile instead of 4 */
    }
}

/* Small Mobile (Max 480px) */
@media (max-width: 480px) {
    .problem-card {
        font-size: 1.1rem;
        padding: 20px 10px;
    }

    .btn-icon,
    .btn-icon-text {
        width: 32px;
        height: 32px;
        font-size: 0.9rem;
        padding: 0 8px;
        /* For icon-text */
    }

    .btn-pill,
    .btn-mode {
        font-size: 0.8rem;
        padding: 6px 10px;
    }

    .setting-grid {
        grid-template-columns: repeat(2, 1fr);
        /* 2 columns on very small screens */
    }
}