:root {
    --bg-body: #2b2a33;
    --text-primary: #e4e4e7;
    --text-secondary: #a1a1aa;

    --btn-bg: #3f3f46;
    --bg-light: rgba(63, 63, 70, .5);
    --btn-border: #52525b;
    --btn-text: #e4e4e7;
    --btn-hover-bg: #52525b;
    --btn-hover-border: #71717a;

    --btn-erase-bg: #3f1d1d;
    --btn-erase-border: #7f1d1d;
    --btn-erase-text: #fca5a5;
    --btn-erase-hover-bg: #4f2020;
    --btn-erase-hover-border: #991b1b;

    --victory-gradient-start: #7c3aed;
    --victory-gradient-end: #a855f7;
    --victory-text: #ffffff;
    --victory-shadow: rgba(124, 58, 237, .5);

    --board-thick-border: #000;
    --board-cell-border: rgba(0, 0, 0, .1);
    --board-bg: #000;
    --board-sum-color: #555;
    --board-select-bg: rgba(0, 0, 0, .3);
    --board-semi-select-bg: rgba(0, 0, 0, .15);
    --board-cage-border: rgba(0, 0, 0, .12);
    --board-num-hint: #111;
    --board-num-correct: #365b9f;
    --board-num-incorrect: #dc093c;
    --board-num-hint-hidden: transparent;
    --board-num-hint-passive: #666;
    --board-num-hint-active: #082114;

    --board-color-0: #FFF6D6;
    --board-color-1: #FFDDE6;
    --board-color-2: #D8F7E0;
    --board-color-3: #E8DEFF;
    --board-color-4: #DCEEFF;
    --board-color-5: #FFF1E0;
    --board-color-6: #F0F0F0;
    --board-color-7: #E8E8E8;
    --board-color-8: #E0E0E0;
    --board-color-9: #D8D8D8;

    --level-easy-bg: var(--board-color-2);
    --level-easy-text: #1a5a3a;
    --level-medium-bg: var(--board-color-0);
    --level-medium-text: #6b5a00;
    --level-hard-bg: var(--board-color-1);
    --level-hard-text: #8b1a3a;
    --level-expert-bg: var(--board-color-3);
    --level-expert-text: #4a2a7a;

    --bg-overlay: rgba(43, 42, 51, .5);
    --shadow-overlay: rgba(0, 0, 0, .85);
}

body {
    font-family: 'Segoe UI', Arial, system-ui, sans-serif;
    margin: 0;
    padding: 12px;
    background: var(--bg-body);
    color: var(--text-primary);
    display: flex;
    justify-content: center;
    box-sizing: border-box;
    overflow-x: hidden;
}

.app {
    max-width: 1100px;
    width: 100%;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 12px;
    box-sizing: border-box;
}

h1 {
    font-size: clamp(1.8rem, 5vw, 2.5rem);
    font-weight: 800;
    margin: 20px 0 10px;
    color: var(--text-primary);
    text-align: center;
    letter-spacing: -0.02em;
    font-variant: small-caps;
}

h2 {
    font-size: clamp(1.2rem, 4vw, 1.5rem);
    font-weight: 700;
    margin: 0 0 12px;
    color: var(--text-primary);
}

kbd {
    font-size: 1.2em;
    color: var(--level-medium-bg);
}

.top-controls {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-between;
    width: 100%;
    box-sizing: border-box;
    max-width: 800px;
    margin-bottom: 1.5rem;
}

.controls-left {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
    align-items: center;
    flex: 1;
}

.lang-btn {
    font-weight: 700;
    min-width: 80px;
    flex-shrink: 0;
}

button {
    padding: 12px 16px;
    border-radius: 8px;
    border: 1px solid var(--btn-border);
    background: var(--btn-bg);
    color: var(--btn-text);
    cursor: pointer;
    font-weight: 700;
    transition: background .2s, border-color .2s;
}

button:hover {
    background: var(--btn-hover-bg);
    border-color: var(--btn-hover-border);
}

.timer-btn {
    min-width: 100px;
    font-variant-numeric: tabular-nums;
}

.timer-btn.active {
    background: var(--victory-gradient-start);
    border-color: var(--victory-gradient-end);
    color: var(--btn-text);
}

.pause-btn {
    background: var(--btn-erase-bg);
    border-color: var(--btn-erase-border);
}

.pause-btn:hover {
    background: var(--btn-erase-hover-bg);
    border-color: var(--btn-erase-hover-border);
}

.pause-btn.paused {
    background: var(--victory-gradient-start);
    border-color: var(--victory-gradient-end);
    color: var(--btn-text);
}

#gen_easy.active {
    background: var(--level-easy-bg);
    border-color: color-mix(in srgb, var(--level-easy-bg) 70%, black);
    color: var(--level-easy-text);
    font-weight: 700;
}

#gen_medium.active {
    background: var(--level-medium-bg);
    border-color: color-mix(in srgb, var(--level-medium-bg) 70%, black);
    color: var(--level-medium-text);
    font-weight: 700;
}

#gen_hard.active {
    background: var(--level-hard-bg);
    border-color: color-mix(in srgb, var(--level-hard-bg) 70%, black);
    color: var(--level-hard-text);
    font-weight: 700;
}

#gen_expert.active {
    background: var(--level-expert-bg);
    border-color: color-mix(in srgb, var(--level-expert-bg) 70%, black);
    color: var(--level-expert-text);
    font-weight: 700;
}

.layout {
    display: flex;
    gap: 12px;
    align-items: flex-start;
    width: 100%;
    justify-content: center;
    position: relative;
}

.board-wrap {
    position: relative;
    width: 100%;
    max-width: 620px;
}

#board {
    display: grid;
    grid-template-columns: repeat(9, 1fr);
    width: 100%;
    aspect-ratio: 1/1;
    background: var(--board-bg);
    box-sizing: border-box;
    padding: 3px;
}

.cell {
    box-sizing: border-box;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 1.5rem;
    user-select: none;
    position: relative;
    cursor: pointer;
    transition: background .12s, transform .06s;
    aspect-ratio: 1/1;
    min-height: 0;
    border-left: 1px solid var(--board-cell-border);
    border-bottom: 1px solid var(--board-cell-border);
}

.cell.block-top {
    border-top: 2px solid var(--board-thick-border) !important;
}

.cell.block-bottom {
    border-bottom: 2px solid var(--board-thick-border) !important;
}

.cell.block-left {
    border-left: 2px solid var(--board-thick-border) !important;
}

.cell.block-right {
    border-right: 2px solid var(--board-thick-border) !important;
}

.cell.cage-top {
    border-top: 2px dashed var(--board-cage-border);
}

.cell.cage-bottom {
    border-bottom: 2px dashed var(--board-cage-border);
}

.cell.cage-left {
    border-left: 2px dashed var(--board-cage-border);
}

.cell.cage-right {
    border-right: 2px dashed var(--board-cage-border);
}

.cell.color-0 {
    background: var(--board-color-0);
}

.cell.color-1 {
    background: var(--board-color-1);
}

.cell.color-2 {
    background: var(--board-color-2);
}

.cell.color-3 {
    background: var(--board-color-3);
}

.cell.color-4 {
    background: var(--board-color-4);
}

.cell.color-5 {
    background: var(--board-color-5);
}

.cell.color-6 {
    background: var(--board-color-6);
}

.cell.color-7 {
    background: var(--board-color-7);
}

.cell.color-8 {
    background: var(--board-color-8);
}

.cell.color-9 {
    background: var(--board-color-9);
}

.cell .num {
    transition: color .12s;
    line-height: 1;
}

.cell .num.hint {
    color: var(--board-num-hint);
}

.cell .num.correct {
    color: var(--board-num-correct);
}

.cell .num.incorrect {
    color: var(--board-num-incorrect);
}

.cell.selected:after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    pointer-events: none;
    background-color: var(--board-select-bg) !important;
}

.cell.semi-selected:after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    pointer-events: none;
    background-color: var(--board-semi-select-bg) !important;
}

.sum {
    position: absolute;
    left: 4px;
    top: 3px;
    font-size: .65rem;
    color: var(--board-sum-color);
    pointer-events: none;
    z-index: 2;
}

.hints-container {
    position: absolute;
    bottom: 2px;
    right: 2px;
    width: 80%;
    height: 80%;
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    grid-template-rows: repeat(3, 1fr);
    gap: 0;
    pointer-events: none;
    z-index: 1;
}

.hint-number {
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: .75rem;
    font-weight: 600;
    color: var(--board-num-hint-hidden);
    transition: color .2s ease;
}

.hint-number.passive {
    color: var(--board-num-hint-passive);
}

.hint-number.active {
    color: var(--board-num-hint-active);
    background-color: var(--board-semi-select-bg);
    font-weight: 700;
}

#panel {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 8px;
    width: 100%;
    max-width: 620px;
    grid-auto-flow: dense;
}

#panel button {
    width: 100%;
    aspect-ratio: 1/1;
    min-width: 0;
    border-radius: 8px;
    border: 1px solid var(--btn-border);
    background: var(--btn-bg);
    color: var(--btn-text);
    font-weight: 700;
    font-size: 1.5rem;
    cursor: pointer;
    box-sizing: border-box;
}

#panel button:hover {
    background: var(--btn-hover-bg);
    border-color: var(--btn-hover-border);
}

#panel .erase {
    background: var(--btn-erase-bg);
    border-color: var(--btn-erase-border);
    color: var(--btn-erase-text);
}

#panel .erase:hover {
    background: var(--btn-erase-hover-bg);
    border-color: var(--btn-erase-hover-border);
}

#panel .hint-btn {
    grid-column: 1 / -1;
    aspect-ratio: auto;
    height: auto;
    min-height: 50px;
    background: var(--btn-bg);
    border-color: var(--btn-border);
    font-size: 1.8rem;
    filter: grayscale(100%);
    opacity: .6;
    transition: filter .3s ease, opacity .3s ease;
}

#panel .hint-btn:hover {
    background: var(--btn-hover-bg);
    border-color: var(--btn-hover-border);
    opacity: .8;
}

#panel .hint-btn.active {
    background: var(--btn-active-bg);
    border-color: var(--btn-active-border);
    filter: grayscale(0%);
    opacity: 1;
}

@media (min-width: 768px) and (orientation: landscape) {
    .layout {
        flex-direction: row;
        align-items: flex-start;
    }

    #panel {
        grid-template-columns: repeat(2, 1fr);
        max-width: 140px;
    }
}

@media (max-width: 767px),
(orientation: portrait) {
    .layout {
        flex-direction: column;
        align-items: center;
    }

    #panel {
        grid-template-columns: repeat(5, 1fr);
    }

    #panel .hint-btn {
        max-width: 200px;
        margin: 0 auto;
    }
}

.victory-panel {
    display: none;
    padding: 16px 24px;
    background: linear-gradient(30deg, var(--victory-gradient-start) 0%, var(--victory-gradient-end) 100%);
    color: var(--victory-text);
    font-size: 1.5rem;
    font-weight: 700;
    border-radius: 12px;
    box-shadow: 0 4px 20px var(--victory-shadow);
    text-align: center;
    animation: victorySlide .5s ease-out;
}

@keyframes victorySlide {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.defeat-panel {
    display: none;
    padding: 16px 24px;
    background: linear-gradient(350deg, #7f1d1d 0%, #450a0a 100%);
    color: var(--victory-text);
    font-size: 1.5rem;
    font-weight: 700;
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(127, 29, 29, .5);
    text-align: center;
    animation: victorySlide .5s ease-out;
}

.victory-panel p,
.defeat-panel p {
    margin: 0;
}

small {
    font-size: .9rem;
}

.rules {
    max-width: 800px;
    width: 100%;
    margin-top: 24px;
    padding: 20px 24px;
    background: var(--bg-light);
    border-radius: 12px;
    border: 1px solid var(--btn-border);
    box-sizing: border-box;
}

.rules-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 12px;
}

.rules-toggle {
    padding: 6px 12px;
    font-size: .9rem;
    font-weight: 600;
    background: var(--btn-bg);
    border: 1px solid var(--btn-border);
    color: var(--btn-text);
    border-radius: 6px;
    cursor: pointer;
    transition: background .2s, border-color .2s;
}

.rules-toggle:hover {
    background: var(--btn-hover-bg);
    border-color: var(--btn-hover-border);
}

.rules-content {
    overflow: hidden;
    transition: max-height .3s ease-out, opacity .3s ease-out;
    max-height: 0;
    opacity: 0;
}

.rules-content.expanded {
    max-height: 100%;
    opacity: 1;
}

.rules ul {
    margin: 0;
    padding-left: 24px;
    list-style-type: disc;
}

.rules li {
    color: var(--text-primary);
    margin-bottom: 8px;
    line-height: 1.6;
}

.rules li:last-child {
    margin-bottom: 0;
}

.pause-overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--bg-overlay);
    backdrop-filter: blur(8px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    border-radius: 12px;
}

.pause-text {
    font-size: 4rem;
    font-weight: 900;
    color: var(--text-primary);
    text-shadow: 0 4px 12px var(--shadow-overlay);
    letter-spacing: .1em;
    animation: pausePulse 2s ease-in-out infinite;
}

@keyframes pausePulse {

    0%,
    100% {
        opacity: 1;
        transform: scale(1);
    }

    50% {
        opacity: .7;
        transform: scale(1.05);
    }
}

@media (max-width: 480px) {
    body {
        padding: 8px;
    }

    .app {
        gap: 8px;
    }

    h1 {
        margin: 10px 0 5px;
    }

    .top-controls {
        gap: 6px;
    }

    .controls-left {
        gap: 6px;
    }

    button {
        padding: 6px;
        font-size: .9rem;
    }

    .timer-btn {
        min-width: 80px;
    }

    .lang-btn {
        min-width: 60px;
    }

    .rules {
        padding: 16px;
        margin-top: 16px;
    }

    .rules-header {
        margin-bottom: 8px;
    }

    .rules-toggle {
        padding: 4px 8px;
        font-size: .8rem;
    }

    .rules ul {
        padding-left: 20px;
        font-size: .9rem;
    }

    .victory-panel {
        padding: 12px 16px;
        font-size: 1.2rem;
    }

    #panel {
        gap: 6px;
    }

    #panel button {
        font-size: 1.3rem;
    }

    .cell {
        font-size: 1.2rem;
    }

    .sum {
        font-size: .55rem;
        left: 2px;
        top: 2px;
    }
}