* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    -webkit-tap-highlight-color: transparent;
}

:root {
    
    --primary-color: #3F51B5;
    --primary-dark: #2029ad;
    --secondary-color: #2ecc71;
    --secondary-dark: #27ae60;
    --secondary-light: #4cd964;
    --accent-color: #e74c3c;
    --note-color: #3F51B5;
    --hint-color: #f1c40f;
    --light-color: #ffffff;
    --light-bg: #f8f9fa;
    --light-border: #e0e0e0;
    --text-color: #333333;
    --text-light: #666666;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
    --shadow-hover: 0 4px 12px rgba(0, 0, 0, 0.12);
}

.dark-theme {
    
    --primary-color: #3f48cc;
    --primary-dark: #2029ad;
    --secondary-color: #27ae60;
    --secondary-dark: #3f48cc;
    --secondary-light: #2ecc71;
    --accent-color: #e74c3c;
    --note-color: #3F51B5;
    --hint-color: #f1c40f;
    --light-color: #1e1e2e;
    --light-bg: #121212;
    --light-border: #2d2d3d;
    --text-color: #f0f0f0;
    --text-light: #b0b0b0;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
    --shadow-hover: 0 4px 12px rgba(0, 0, 0, 0.4);
}

body {
    background-color: var(--light-bg);
    color: var(--text-color);
    min-height: 100vh;
    padding: 15px;
    transition: background-color 0.3s, color 0.3s;
    position: relative;
    overflow-x: hidden;
}

body.android-app .container {
    margin-top: env(safe-area-inset-top, 38px);
}

.container {
    display: flex;
    flex-direction: column;
    align-items: center;
    max-width: 1300px;
    width: 100%;
    margin: 0 auto;
}


.header {
    display: flex;
    flex-direction: column;
    margin-bottom: 20px;
    padding-bottom: 15px;
    border-bottom: 2px solid var(--light-border);
    gap: 15px;
    width: 100%;
    position: relative;
}

.header-top {
    display: flex;
    justify-content: space-between;
    align-items: center;
    width: 100%;
    position: relative;
}

.logo-section {
    display: flex;
    align-items: center;
    gap: 10px;
    flex: 1;
}

.logo-img img {
    height: 40px;
    width: auto;
}

.theme-toggle-absolute {
    position: absolute;
    right: 0;
    top: 0;
    z-index: 10;
}

.theme-btn {
    color: var(--text-color);
    padding: 8px;
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 44px;
    height: 44px;
    text-decoration: none;
}

.theme-btn:hover {
    transform: rotate(30deg);
    border: none;
    background-color: transparent;
    box-shadow: none;
}

#themeIcon {
    font-size: 1.4rem;
    display: flex;
    align-items: center;
    justify-content: center;
}

.game-info-container {
    display: flex;
    flex-direction: column;
    gap: 15px;
    width: 100%;
}




.difficulty-buttons {
    display: flex;
    justify-content: center;
    gap: 10px;
    margin-bottom: 15px;
    flex-wrap: wrap;
}

.difficulty-btn {
    padding: 12px 20px;
    border: 2px solid var(--light-border);
    background-color: var(--light-color);
    border-radius: 8px;
    font-weight: 600;
    color: var(--text-color);
    cursor: pointer;
    transition: all 0.2s ease;
    text-align: center;
    font-size: 0.95rem;
    text-decoration: none;
    flex: 1;
    min-width: 100px;
    max-width: 150px;
}

.difficulty-btn:hover {
    border-color: var(--primary-color);
    background-color: rgba(52, 152, 219, 0.1);
}

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


.game-main-container {
    display: flex;
    flex-direction: column;
    gap: 10px;
    width: max-content;
    flex: 1;
}


.game-board-container {
    width: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    overflow: auto;
}

.game-board {
    width: 100%;
    display: flex;
    justify-content: center;
    overflow: visible;
    position: relative;
}

.sudoku-grid {
    border-collapse: collapse;
    background-color: var(--light-color);
    border: 3px solid #545454;
    margin: 0 auto;
    width: inherit;
    position: relative;
    z-index: 10;
}

.dark-theme .sudoku-grid {
    border-color: #bababa;
}

.sudoku-cell {
    border: 1.5px solid #bbbbbb;
    text-align: center;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.15s ease;
    position: relative;
    background-color: var(--light-color);
    user-select: none;
}

.dark-theme .sudoku-cell {
    border-color: #4a5568;
}


.sudoku-grid .sudoku-cell {
    width: 55px;
    height: 55px;
    font-size: 2.5rem;
}

.sudoku-cell.filled {
    color: var(--text-color);
    font-weight: 400;
}

.sudoku-cell.user-filled {
    color: var(--secondary-light);
}

.sudoku-cell.selected {
    background-color: rgb(52 152 219 / 26%);
}

.sudoku-cell.highlighted {
    background-color: rgba(255, 204, 0, 0.1);
}

.sudoku-cell.same-number {
    background-color: rgba(231, 76, 60, 0.15);
    color: #c0392b;
}

.sudoku-cell.highlight-row-col {
    background-color: rgba(52, 152, 219, 0.08);
}

.sudoku-cell.error {
    background-color: rgba(231, 76, 60, 0.2);
    color: #c0392b;
}

.sudoku-cell.validation-error {
    background-color: #e74c3c !important;
    color: white !important;
}

.sudoku-cell.hint {
    background-color: rgba(241, 196, 15, 0.15);
    border-color: var(--hint-color);
}


.notes-container {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    grid-template-rows: repeat(3, 1fr);
    gap: 1px;
    padding: 1px;
    pointer-events: none;
    box-sizing: border-box;
}

.note {
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    color: var(--note-color);
    font-weight: 600;
    opacity: 0.8;
    overflow: hidden;
    text-overflow: ellipsis;
    line-height: 1;
    padding: 0;
    margin: 0;
}


.sudoku-grid tr:nth-child(3n):not(:last-child) td {
    border-bottom: 2px solid #686868;
}

.sudoku-grid td:nth-child(3n):not(:last-child) {
    border-right: 2.3px solid #707070;
}


.dark-theme .sudoku-grid {
    border-color: #9E9E9E;
}

.dark-theme .sudoku-cell {
    border: 1.5px solid #484848;
}


.dark-theme .sudoku-grid tr:nth-child(3n):not(:last-child) td {
    border-bottom: 2px solid #9E9E9E;
}

.dark-theme .sudoku-grid td:nth-child(3n):not(:last-child) {
    border-right: 2.3px solid #9E9E9E;
}


.control-panel {
    width: 100%;
    max-width: 600px;
    margin: 0 auto;
    padding: 0 10px;
}

.control-card {
    display: flex;
    flex-direction: column;
    gap: 15px;
}

.tool-buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 15px;
}

.tool-btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 15px 0;
    border: 2px solid var(--light-border);
    background-color: transparent;
    cursor: pointer;
    transition: all 0.2s ease;
    text-align: center;
    border-radius: 12px;
    text-decoration: none;
    color: inherit;
    min-height: 80px;
}

.tool-btn:hover, .tool-btn.active {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
    transform: translateY(-2px);
}

.tool-btn.pressed {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
    transform: translateY(-2px);
}

.tool-btn.note-mode.active {
    background-color: var(--note-color);
    border-color: var(--note-color);
}

.dark-theme .tool-btn.note-mode.active {
    background-color: var(--note-color);
    border-color: var(--note-color);
    color: white;
}

.tool-icon {
    font-size: 1.8rem;
    margin-bottom: 5px;
}


.number-pad {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 10px;
}

.number-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    border: 2px solid var(--light-border);
    background-color: var(--light-color);
    cursor: pointer;
    transition: all 0.2s ease;
    font-size: 1.5rem;
    color: var(--primary-color);
    text-decoration: none;
    aspect-ratio: 1 / 1;
    border-radius: 10px;
    font-weight: 600;
    user-select: none;
}

.number-btn:hover, .number-btn:active {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
    transform: scale(1.05);
}

.number-btn.pressed {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
    transform: scale(1.05);
}

.new-game-container {
}

.new-game-btn {
    width: 100%;
    padding: 18px;
    background-color: var(--secondary-color);
    border: none;
    border-radius: 12px;
    color: white;
    font-size: 1.2rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    text-decoration: none;
    display: block;
    text-align: center;
    user-select: none;
}

.dark-theme .new-game-btn {
    background-color: var(--secondary-dark);
}

.new-game-btn:hover, .new-game-btn:active {
    background-color: var(--secondary-dark);
    transform: translateY(-3px);
}

.dark-theme .new-game-btn:hover {
    background-color: var(--secondary-dark);
}


.desktop-number-panel {
    display: none;
}


.desktop-tool-buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    margin-bottom: 20px;
}

.desktop-tool-btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: initial;
    padding: 10px;
    border: 2px solid var(--light-border);
    background-color: transparent;
    cursor: pointer;
    transition: all 0.2s ease;
    text-align: center;
    border-radius: 12px;
    text-decoration: none;
    color: inherit;
    min-height: 80px;
    min-width: 80px;
}

.desktop-tool-btn:hover, .desktop-tool-btn.active {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
    transform: translateY(-2px);
}

.desktop-tool-btn.pressed {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
    transform: translateY(-2px);
}

.desktop-tool-btn.note-mode.active {
    background-color: var(--note-color);
    border-color: var(--note-color);
}

.dark-theme .desktop-tool-btn.note-mode.active {
    background-color: var(--note-color);
    border-color: var(--note-color);
    color: white;
}

.desktop-tool-icon {
    font-size: 1.8rem;
    margin-bottom: 5px;
}

.desktop-tool-btn-label {
    font-size: 0.8rem;
}

.desktop-number-pad {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 12px;
    width: 100%;
}

.desktop-number-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    border: 2px solid var(--light-border);
    background-color: var(--light-color);
    cursor: pointer;
    transition: all 0.2s ease;
    font-size: 1.6rem;
    color: var(--primary-color);
    text-decoration: none;
    aspect-ratio: 1 / 1;
    border-radius: 12px;
    font-weight: 400;
    user-select: none;
}

.desktop-number-btn:hover, .desktop-number-btn:active {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
    transform: scale(1.05);
}

.desktop-number-btn.pressed {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
    transform: scale(1.05);
}


.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: rgba(0, 0, 0, 0.7);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s ease;
    padding: 20px;
}

.modal-overlay.active {
    opacity: 1;
    visibility: visible;
}

.modal {
    background-color: var(--light-color);
    border-radius: 15px;
    padding: 25px;
    max-width: 500px;
    width: 100%;
    text-align: center;
    box-shadow: 0 15px 30px rgba(0, 0, 0, 0.2);
    transform: translateY(20px);
    transition: transform 0.3s ease;
}

.modal-overlay.active .modal {
    transform: translateY(0);
}

.modal-icon {
    font-size: 3rem;
    color: var(--secondary-color);
    margin-bottom: 15px;
}

.dark-theme .modal-icon {
    color: var(--secondary-light);
}

.modal h2 {
    color: var(--primary-color);
    margin-bottom: 10px;
    font-size: 1.6rem;
}

.modal p {
    color: var(--text-light);
    margin-bottom: 20px;
    font-size: 0.95rem;
    line-height: 1.5;
}

.modal-stats {
    display: flex;
    grid-template-columns: repeat(2, 1fr);
    gap: 15px;
    margin: 20px 0;
    padding: 15px 0;
    border-top: 1px solid var(--light-border);
    border-bottom: 1px solid var(--light-border);
    justify-content: center;
}

.stat-item h4 {
    color: var(--text-light);
    font-size: 0.8rem;
    margin-bottom: 5px;
}

.modal-stat-value {
    font-size: 1.5rem;
    color: var(--primary-color);
    text-align: center;
}

.modal-close-btn {
    background-color: var(--primary-color);
    border: none;
    color: white;
    padding: 15px;
    font-size: 1.1rem;
    font-weight: 600;
    border-radius: 10px;
    cursor: pointer;
    transition: all 0.2s ease;
    margin-top: 10px;
    width: 100%;
    text-decoration: none;
    display: block;
}

.modal-close-btn:hover {
    background-color: var(--primary-dark);
}


.hint-message {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background-color: var(--hint-color);
    color: #333;
    padding: 15px 20px;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
    z-index: 100;
    opacity: 0;
    transition: all 0.3s ease;
    max-width: 300px;
    text-align: center;
    pointer-events: none; 
}

.hint-message.show {
    opacity: 1;
    transform: translate(-50%, -50%);
}

footer {
    margin-top: 20px;
    text-align: center;
    color: var(--text-light);
    font-size: 0.8rem;
    padding: 15px 0;
    border-top: 1px solid var(--light-border);
    width: 100%;
}


.dark-theme .number-btn,
.dark-theme .desktop-number-btn {
    background-color: #2d2d3d;
    border-color: #3d3d4d;
    color: white;
}

.dark-theme .number-btn.pressed,
.dark-theme .desktop-number-btn.pressed {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
}

.dark-theme .tool-btn,
.dark-theme .desktop-tool-btn {
    background-color: #2d2d3d;
    border-color: #3d3d4d;
}

.dark-theme .tool-btn.pressed,
.dark-theme .desktop-tool-btn.pressed {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
}

.dark-theme .difficulty-btn {
    background-color: #2d2d3d;
    border-color: #3d3d4d;
    display: flex;
    justify-content: center;
}

.dark-theme .difficulty-btn.active {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
}


@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

@keyframes slideUp {
    from { transform: translateY(20px); opacity: 0; }
    to { transform: translateY(0); opacity: 1; }
}

.modal {
    animation: slideUp 0.3s ease;
}


.game-board {
    -webkit-overflow-scrolling: touch;
}