/* ===== Variables & Base ===== */
:root {
    --bg-dark: #0f1419;
    --bg-card: #1a2332;
    --bg-cell: #243447;
    --bg-cell-hover: #2d3f54;
    --border-grid: #3d5568;
    --border-box: #4a6572;
    --text-primary: #e7e9ea;
    --text-muted: #8b98a5;
    --accent: #1d9bf0;
    --accent-hover: #1a8cd8;
    --success: #00ba7c;
    --error: #f4212e;
    --given-color: #e7e9ea;
    --user-color: #78b4fa;
    --note-color: #8b98a5;
    --killer-cage-stroke: rgba(100, 125, 145, 0.92);
    --navbar-bg: rgba(26, 35, 50, 0.95);
    --navbar-border: rgba(61, 85, 104, 0.5);
    --bg-gradient-start: #0f1419;
    --bg-gradient-mid: #1a2332;
    --bg-gradient-end: #0f1419;
}

/* Light theme */
[data-theme="light"] {
    --bg-dark: #eef2f5;
    --bg-card: #ffffff;
    --bg-cell: #f0f4f8;
    --bg-cell-hover: #e2e8f0;
    --border-grid: #cbd5e1;
    --border-box: #94a3b8;
    --text-primary: #1e293b;
    --text-muted: #64748b;
    --accent: #0ea5e9;
    --accent-hover: #0284c7;
    --success: #059669;
    --error: #dc2626;
    --given-color: #1e293b;
    --user-color: #2563eb;
    --note-color: #64748b;
    --killer-cage-stroke: rgba(71, 85, 105, 0.92);
    --navbar-bg: rgba(255, 255, 255, 0.98);
    --navbar-border: rgba(203, 213, 225, 0.8);
    --bg-gradient-start: #eef2f5;
    --bg-gradient-mid: #ffffff;
    --bg-gradient-end: #eef2f5;
}

[data-theme="light"] .text-white {
    color: var(--text-primary) !important;
}
[data-theme="light"] .text-white-50 {
    color: var(--text-muted) !important;
}

.text-accent {
    color: var(--accent);
}

* {
    box-sizing: border-box;
}

body {
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
    background: var(--bg-dark);
    color: var(--text-primary);
    min-height: 100vh;
}

body.game-page,
body.home-page {
    background: linear-gradient(160deg, var(--bg-gradient-start) 0%, var(--bg-gradient-mid) 50%, var(--bg-gradient-end) 100%);
}

/* ===== Home landing hero ===== */
.home-main {
    overflow-x: clip;
}

.home-hero-band {
    width: 100vw;
    max-width: 100vw;
    margin-left: calc(50% - 50vw);
    margin-right: calc(50% - 50vw);
    border-bottom: 1px solid var(--navbar-border);
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.04);
    background: linear-gradient(168deg, #121923 0%, var(--bg-card) 40%, #101820 100%);
}

[data-theme="light"] .home-hero-band {
    background: linear-gradient(168deg, #d8e0ea 0%, #ffffff 45%, #e4eaf2 100%);
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.9);
}

.home-hero-inner {
    padding-top: 2.5rem;
    padding-bottom: 2.5rem;
}

@media (min-width: 992px) {
    .home-hero-inner {
        padding-top: 3.5rem;
        padding-bottom: 3.75rem;
    }
}

.home-hero-glow {
    position: absolute;
    inset: -35% -15% auto -15%;
    height: min(75vh, 560px);
    background: radial-gradient(ellipse 72% 58% at 72% 18%, rgba(29, 155, 240, 0.22), transparent 68%);
    pointer-events: none;
}

[data-theme="light"] .home-hero-glow {
    background: radial-gradient(ellipse 72% 58% at 72% 18%, rgba(14, 165, 233, 0.14), transparent 68%);
}

.home-hero-heading {
    font-size: clamp(1.85rem, 4vw + 1rem, 3rem);
    line-height: 1.15;
    letter-spacing: -0.02em;
    text-shadow: 0 2px 24px rgba(0, 0, 0, 0.35);
}

[data-theme="light"] .home-hero-heading {
    text-shadow: 0 1px 0 rgba(255, 255, 255, 0.9);
}

.home-hero-lead {
    font-size: clamp(1.05rem, 0.6vw + 0.95rem, 1.28rem);
    font-weight: 500;
    line-height: 1.5;
    max-width: 38rem;
    margin-left: auto;
    margin-right: auto;
}

@media (min-width: 768px) {
    .home-hero-lead {
        margin-left: 0;
        margin-right: 0;
    }
}

.home-hero-sub {
    font-size: 0.98rem;
    line-height: 1.6;
    max-width: 36rem;
    margin-left: auto;
    margin-right: auto;
    opacity: 0.95;
}

@media (min-width: 768px) {
    .home-hero-sub {
        margin-left: 0;
        margin-right: 0;
    }
}

.home-hero-eyebrow {
    font-size: 0.72rem;
    letter-spacing: 0.14em;
    text-transform: uppercase;
    font-weight: 700;
    color: var(--accent);
}

.home-hero-badge {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    justify-content: center;
}

@media (min-width: 768px) {
    .home-hero-badge {
        justify-content: flex-start;
    }
}

.home-hero-badge-pill {
    display: inline-flex;
    align-items: center;
    padding: 0.35rem 0.75rem;
    border-radius: 999px;
    background: var(--bg-card);
    border: 1px solid var(--border-grid);
    color: var(--text-muted);
    font-weight: 500;
}

.home-hero-band .home-hero-badge-pill {
    background: rgba(36, 52, 71, 0.55);
    border-color: rgba(61, 85, 104, 0.65);
}

[data-theme="light"] .home-hero-band .home-hero-badge-pill {
    background: rgba(255, 255, 255, 0.78);
    border-color: var(--border-grid);
}

/* Hero CTAs: Bootstrap btn-light / btn-outline-light are for dark bands; on light gradient they wash out */
[data-theme="light"] .home-hero-band .btn.btn-light {
    background: linear-gradient(135deg, #0ea5e9, #38bdf8);
    color: #fff !important;
    border: 2px solid transparent;
    box-shadow: 0 2px 12px rgba(14, 165, 233, 0.25);
}

[data-theme="light"] .home-hero-band .btn.btn-light:hover {
    background: linear-gradient(135deg, #0284c7, #0ea5e9);
    color: #fff !important;
    border-color: transparent;
    box-shadow: 0 4px 18px rgba(14, 165, 233, 0.35);
}

[data-theme="light"] .home-hero-band .btn.btn-outline-light {
    background: rgba(255, 255, 255, 0.92);
    color: #0f172a !important;
    border: 2px solid rgba(15, 23, 42, 0.28);
    box-shadow: 0 1px 3px rgba(15, 23, 42, 0.06);
}

[data-theme="light"] .home-hero-band .btn.btn-outline-light:hover {
    background: #fff;
    color: #0f172a !important;
    border-color: var(--accent);
    box-shadow: 0 4px 14px rgba(14, 165, 233, 0.2);
}

[data-theme="light"] .home-hero-band .home-hero-heading.text-white {
    color: #0f172a !important;
}

[data-theme="light"] .home-hero-band .home-hero-lead.text-white-50,
[data-theme="light"] .home-hero-band .home-hero-sub.text-white-50 {
    color: #334155 !important;
}

[data-theme="light"] .home-hero-band .home-hero-badge.text-white-50 {
    color: #475569 !important;
}

[data-theme="light"] .home-hero-band .home-hero-figure .text-white {
    color: #0f172a !important;
}

[data-theme="light"] .home-hero-band .home-hero-figure .text-white-50 {
    color: #64748b !important;
}

.home-hero-figure {
    width: min(100%, 340px);
}

.home-hero-figure-caption {
    text-align: center;
    max-width: 300px;
    margin-left: auto;
    margin-right: auto;
    line-height: 1.45;
}

.home-hero-figure-caption .fa-info-circle {
    color: var(--accent);
    opacity: 0.85;
}

.home-hero-figure-frame {
    padding: 1.35rem 1.35rem 1.15rem;
    background: var(--bg-dark);
    border: 1px solid var(--border-grid);
    border-radius: 20px;
    box-shadow:
        0 16px 48px rgba(0, 0, 0, 0.35),
        0 0 0 1px rgba(255, 255, 255, 0.03) inset;
}

[data-theme="light"] .home-hero-figure-frame {
    background: var(--bg-cell);
    box-shadow:
        0 16px 40px rgba(15, 23, 42, 0.1),
        0 0 0 1px rgba(255, 255, 255, 0.8) inset;
}

.home-hero-sudoku-svg {
    display: block;
    width: 100%;
    max-width: 300px;
    height: auto;
    margin: 0 auto;
    border-radius: 6px;
}

.home-hero-svg-digits text {
    paint-order: stroke fill;
}

/* ===== Home page below hero ===== */
.home-below {
    padding-top: 2.25rem;
    padding-bottom: 3rem;
}

@media (min-width: 992px) {
    .home-below {
        padding-top: 2.75rem;
        padding-bottom: 3.5rem;
    }
}

.home-below-measure {
    max-width: 720px;
    margin-left: auto;
    margin-right: auto;
}

.home-below-section {
    margin-top: 2.25rem;
    padding-top: 2.25rem;
    border-top: 1px solid var(--navbar-border);
}

.home-below-section h2 {
    margin-bottom: 1.25rem;
}

.home-below-label {
    font-size: 0.72rem;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    font-weight: 700;
    color: var(--accent);
    margin-bottom: 0.65rem;
    text-align: center;
}

@media (min-width: 992px) {
    .home-below-intro.text-lg-start .home-below-label {
        text-align: left;
    }
}

.home-below-chips {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem 0.65rem;
    justify-content: center;
}

@media (min-width: 992px) {
    .home-below-intro.text-lg-start .home-below-chips {
        justify-content: flex-start;
    }
}

.home-below-chip {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    padding: 0.48rem 0.95rem;
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-primary);
    background: var(--bg-card);
    border: 1px solid var(--border-grid);
    border-radius: 999px;
    text-decoration: none;
    transition: border-color 0.2s, color 0.2s, background 0.2s, box-shadow 0.2s;
}

.home-below-chip:hover {
    border-color: var(--accent);
    color: var(--accent);
    background: var(--bg-cell-hover);
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.12);
}

[data-theme="light"] .home-below-chip:hover {
    box-shadow: 0 2px 12px rgba(15, 23, 42, 0.06);
}

.home-below-chip i {
    font-size: 0.88rem;
    color: var(--accent);
    opacity: 0.9;
}

.home-below-card-row {
    display: flex;
    flex-direction: column;
    flex-wrap: wrap;
    gap: 0.85rem;
    justify-content: center;
    text-align: left;
}

@media (min-width: 576px) {
    .home-below-card-row {
        flex-direction: row;
    }
}

.home-below-actions {
    margin-top: 1.35rem;
}

.home-below-actions .btn-print-home--outline.btn-sm {
    padding: 0.4rem 0.95rem;
    font-size: 0.8125rem;
}

/* ===== Site footer ===== */
.site-footer {
    margin-top: auto;
    background: var(--bg-card);
    border-color: var(--navbar-border) !important;
    color: var(--text-muted);
}

.site-footer a {
    color: var(--text-muted);
    text-decoration: none;
    transition: color 0.15s ease;
}

.site-footer a:hover {
    color: var(--accent);
}

.site-footer-heading {
    font-size: 0.72rem;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 0.85rem;
}

.site-footer-heading--row {
    display: block;
    width: 100%;
    margin-bottom: 0.75rem;
}

.site-footer-blocks {
    display: flex;
    flex-direction: column;
    gap: 1.75rem;
}

.site-footer-block {
    width: 100%;
}

.site-footer-list li {
    margin-bottom: 0.45rem;
}

.site-footer-list li:last-child {
    margin-bottom: 0;
}

.site-footer-list--grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 0.5rem 1.25rem;
    text-align: start;
}

.site-footer-list--grid li {
    margin-bottom: 0;
}

@media (min-width: 576px) {
    .site-footer-list--grid {
        grid-template-columns: repeat(3, minmax(0, 1fr));
    }
}

@media (min-width: 992px) {
    .site-footer-list--grid {
        grid-template-columns: repeat(4, minmax(0, 1fr));
    }
}

@media (min-width: 992px) {
    .site-footer-list--two-col {
        columns: 2;
        column-gap: 2rem;
    }

    .site-footer-list--two-col li {
        break-inside: avoid;
    }
}

.site-footer-rule {
    margin: 0;
    border: 0;
    border-top: 1px solid var(--border-grid);
    opacity: 1;
}

.site-footer-copy {
    color: var(--text-primary);
    font-weight: 600;
}

.site-footer-tagline {
    color: var(--text-muted);
    font-size: 0.9rem;
}

.site-footer-heart {
    color: #f43f5e;
    display: inline-block;
}

[data-theme="light"] .site-footer-heart {
    color: #e11d48;
}

/* ===== Navbar ===== */
.navbar {
    background: var(--navbar-bg) !important;
    border-bottom: 1px solid var(--navbar-border);
}

.navbar-brand {
    color: var(--text-primary) !important;
}

.navbar .btn,
.navbar .navbar-theme-toggle {
    color: var(--text-primary) !important;
    border-color: var(--border-grid);
}
.navbar .btn:hover,
.navbar .navbar-theme-toggle:hover {
    border-color: var(--accent) !important;
    color: var(--accent) !important;
}

/* Theme toggle */
.navbar-theme-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 2.5rem;
    height: 2.5rem;
    padding: 0;
    border-radius: 50%;
    border: 1px solid;
    background: transparent;
    cursor: pointer;
    transition: background 0.2s, border-color 0.2s, color 0.2s;
}
.navbar-theme-toggle:hover {
    background: var(--bg-cell-hover);
}
.navbar-theme-toggle i {
    font-size: 1.1rem;
}
.navbar-theme-toggle .icon-sun { display: none; }
.navbar-theme-toggle .icon-moon { display: inline-block; }
[data-theme="light"] .navbar-theme-toggle .icon-sun { display: inline-block; }
[data-theme="light"] .navbar-theme-toggle .icon-moon { display: none; }

/* ===== Home page difficulty buttons ===== */
.btn-difficulty {
    border-radius: 12px;
    font-weight: 600;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
    border: 2px solid transparent;
}

.btn-difficulty:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.3);
}

.btn-difficulty.EASY {
    background: linear-gradient(135deg, #00ba7c, #00d68f);
    color: #fff;
}

.btn-difficulty.MEDIUM {
    background: linear-gradient(135deg, #1d9bf0, #4db8f5);
    color: #fff;
}

.btn-difficulty.HARD {
    background: linear-gradient(135deg, #f59e0b, #fbbf24);
    color: #1a1a1a;
}

.btn-difficulty.EXPERT {
    background: linear-gradient(135deg, #ef4444, #f87171);
    color: #fff;
}

.btn-difficulty--home {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.45rem;
    min-height: 3.35rem;
    min-width: min(100%, 9.25rem);
    padding: 0.7rem 1.35rem;
    font-size: 1.06rem;
    letter-spacing: 0.01em;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.18);
}

.btn-difficulty--home:hover {
    box-shadow: 0 10px 28px rgba(0, 0, 0, 0.28);
}

.btn-difficulty-home-inner {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

.btn-difficulty-icon {
    font-size: 1.08rem;
    opacity: 0.95;
}

/* Home: Printable Sudoku button – visible in light and dark theme */
.btn-print-home {
    background: linear-gradient(135deg, #1d9bf0, #4db8f5);
    color: #fff !important;
    border: 2px solid transparent;
    border-radius: 10px;
    font-weight: 600;
    padding: 0.5rem 1.1rem;
    text-decoration: none;
    display: inline-block;
    transition: transform 0.2s, box-shadow 0.2s, background 0.2s, border-color 0.2s, color 0.2s;
}

.btn-print-home:hover {
    color: #fff !important;
    background: linear-gradient(135deg, #1a8cd8, #1d9bf0);
    transform: translateY(-1px);
    box-shadow: 0 4px 16px rgba(29, 155, 240, 0.4);
}

.btn-print-home--outline {
    background: transparent;
    color: var(--accent) !important;
    border-color: var(--accent);
    box-shadow: none;
}

.btn-print-home--outline:hover {
    color: #fff !important;
    background: linear-gradient(135deg, #1d9bf0, #4db8f5);
    border-color: transparent;
    box-shadow: 0 6px 20px rgba(29, 155, 240, 0.35);
}

[data-theme="light"] .btn-print-home--outline {
    background: rgba(255, 255, 255, 0.35);
}

[data-theme="light"] .btn-print-home--outline:hover {
    background: linear-gradient(135deg, #0ea5e9, #38bdf8);
}

/* ===== Stats ===== */
.stat-box {
    background: var(--bg-card);
    padding: 0.6rem 1.2rem;
    border-radius: 10px;
    font-weight: 600;
    color: var(--text-primary);
    border: 1px solid var(--border-grid);
    display: inline-flex;
    align-items: center;
}

.stat-box i {
    color: var(--accent);
}

/* ===== Sudoku grid ===== */
.sudoku-wrapper {
    background: var(--bg-card);
    padding: 1rem;
    border-radius: 16px;
    border: 1px solid var(--border-grid);
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
}

.sudoku-grid {
    display: grid;
    /* minmax(0, 1fr) keeps row/column heights stable when cell content (digits) appears — avoids implicit auto rows growing */
    grid-template-columns: repeat(9, minmax(0, 1fr));
    grid-template-rows: repeat(9, minmax(0, 1fr));
    gap: 0;
    width: min( min(90vw, 450px), 450px );
    aspect-ratio: 1;
    margin: 0 auto;
    border: 2px solid var(--border-box);
    border-radius: 8px;
    overflow: hidden;
}

.sudoku-grid > .cell {
    min-width: 0;
    min-height: 0;
}

/* Killer: outer board holds 9×9 grid + overlay SVG (SVG must NOT be a grid child of #sudoku-grid) */
.killer-grid-board {
    position: relative;
    width: min(min(90vw, 450px), 450px);
    aspect-ratio: 1;
    margin: 0 auto;
    border: 2px solid var(--border-box);
    border-radius: 8px;
    overflow: hidden;
}

.killer-grid-board #sudoku-grid.sudoku-grid {
    width: 100%;
    height: 100%;
    margin: 0;
    border: none;
    border-radius: 0;
    position: relative;
    z-index: 1;
}

.killer-grid-board .killer-cage-svg {
    position: absolute;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    z-index: 5;
    pointer-events: none;
    overflow: visible;
}

.cell {
    background: var(--bg-cell);
    border: 1px solid var(--border-grid);
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    cursor: pointer;
    transition: background 0.15s ease, transform 0.1s ease;
    font-size: clamp(14px, 4vw, 22px);
    font-weight: 600;
}

.cell:hover:not(.given) {
    background: var(--bg-cell-hover);
}

.cell.selected {
    background: rgba(29, 155, 240, 0.35);
    outline: 2px solid var(--accent);
    outline-offset: -2px;
    z-index: 1;
}

.cell.same-number {
    background: rgba(29, 155, 240, 0.15);
}

.cell.error {
    background: rgba(244, 33, 46, 0.2);
    animation: shake 0.4s ease;
}

.cell.given .cell-value {
    color: var(--given-color);
}

.cell:not(.given) .cell-value {
    color: var(--user-color);
}

.cell-value {
    position: relative;
    z-index: 2;
    line-height: 1;
}

/* 3x3 box borders */
.cell:nth-child(3n) {
    border-right-width: 2px;
    border-right-color: var(--border-box);
}

.cell:nth-child(n+19):nth-child(-n+27),
.cell:nth-child(n+46):nth-child(-n+54) {
    border-bottom-width: 2px;
    border-bottom-color: var(--border-box);
}

.cell:nth-child(9n) {
    border-right-width: 2px;
    border-right-color: var(--border-box);
}

/* Notes inside cell */
.cell-notes {
    position: absolute;
    inset: 2px;
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    grid-template-rows: repeat(3, 1fr);
    font-size: 0.5em;
    color: var(--note-color);
    align-items: center;
    justify-items: center;
    pointer-events: none;
}

.cell-notes span {
    font-weight: 600;
    font-size: clamp(8px, 0.75em, 12px);
}

/* Killer cages: dashed SVG paths sit above cell fills so strokes are visible (cf. sudoku.com/killer) */
.killer-cage-path {
    fill: none;
    stroke: var(--killer-cage-stroke);
    stroke-width: 1.35px;
    stroke-dasharray: 2px 3.5px;
    stroke-linecap: round;
    stroke-linejoin: round;
    vector-effect: non-scaling-stroke;
}

/* Halo so digits stay readable where a dashed cage line crosses */
.killer-grid-board .cell-value {
    text-shadow:
        0 0 1px var(--bg-cell),
        0 0 4px var(--bg-cell),
        0 0 8px var(--bg-cell);
}

.killer-grid-board .cell-notes span {
    text-shadow:
        0 0 1px var(--bg-cell),
        0 0 3px var(--bg-cell);
}

.killer-sum {
    position: absolute;
    top: 2px;
    left: 3px;
    z-index: 3;
    font-size: clamp(8px, 2.5vw, 11px);
    font-weight: 600;
    line-height: 1.1;
    letter-spacing: -0.02em;
    color: var(--given-color);
    opacity: 0.88;
    pointer-events: none;
}

.killer-grid-board .killer-sum {
    text-shadow:
        0 0 1px var(--bg-cell),
        0 0 4px var(--bg-cell);
}

.killer-grid .cell {
    overflow: visible;
}

/* ===== Actions ===== */
.actions-bar {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem;
    justify-content: center;
}

.btn-action {
    background: var(--bg-card);
    color: var(--text-primary);
    border: 1px solid var(--border-grid);
    border-radius: 10px;
    padding: 0.6rem 1rem;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    transition: background 0.2s, transform 0.15s, border-color 0.2s;
}

.btn-action:hover {
    background: var(--bg-cell-hover);
    border-color: var(--accent);
    color: var(--accent);
    transform: translateY(-1px);
}

.btn-action.active {
    background: rgba(29, 155, 240, 0.25);
    border-color: var(--accent);
    color: var(--accent);
}

.btn-action:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none;
}

/* ===== Number pad ===== */
.numpad {
    display: grid;
    grid-template-columns: repeat(9, 1fr);
    gap: 0.4rem;
    max-width: 450px;
    margin-left: auto;
    margin-right: auto;
}

.numpad-btn {
    aspect-ratio: 1;
    border-radius: 10px;
    border: 1px solid var(--border-grid);
    background: var(--bg-card);
    color: var(--text-primary);
    font-weight: 700;
    font-size: 1.1rem;
    cursor: pointer;
    transition: background 0.15s, transform 0.1s, border-color 0.15s;
}

.numpad-btn:hover {
    background: var(--bg-cell-hover);
    border-color: var(--accent);
    color: var(--accent);
    transform: scale(1.05);
}

.numpad-btn:active {
    transform: scale(0.98);
}

/* ===== New game buttons ===== */
.btn-new-game {
    background: var(--bg-card);
    color: var(--text-primary);
    border: 1px solid var(--border-grid);
    border-radius: 8px;
    padding: 0.4rem 0.9rem;
    font-size: 0.9rem;
    transition: background 0.2s, border-color 0.2s;
}

.btn-new-game:hover {
    background: var(--bg-cell-hover);
    border-color: var(--accent);
    color: var(--accent);
}

/* ===== Win modal ===== */
.modal-win .modal-content {
    background: var(--bg-card);
    border: 1px solid var(--border-box);
    border-radius: 16px;
}

.modal-win.modal-correct .modal-content {
    border-color: rgba(0, 186, 124, 0.5);
    box-shadow: 0 0 40px rgba(0, 186, 124, 0.2);
}

.modal-win.modal-wrong .modal-content {
    border-color: rgba(244, 33, 46, 0.4);
    box-shadow: 0 0 30px rgba(244, 33, 46, 0.15);
}

/* Celebration sparkles (correct solution) */
.sparkles-container {
    position: absolute;
    inset: 0;
    pointer-events: none;
    overflow: visible;
    border-radius: 16px;
}

.sparkle {
    position: absolute;
    width: 8px;
    height: 8px;
    border-radius: 50%;
    left: 50%;
    top: 50%;
    opacity: 0;
    animation: sparkle-burst 1.2s ease-out forwards;
}

.sparkle.star {
    width: 0;
    height: 0;
    background: none;
    border-radius: 0;
    box-shadow: none;
}

.sparkle.star::before {
    content: '\2605';
    position: absolute;
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);
    font-size: 12px;
    color: #fbbf24;
    opacity: 0;
    animation: sparkle-star 1.2s ease-out forwards;
}

@keyframes sparkle-burst {
    0% {
        transform: translate(-50%, -50%) scale(0);
        opacity: 1;
    }
    30% {
        transform: translate(-50%, -50%) scale(1);
        opacity: 1;
    }
    100% {
        transform: translate(calc(-50% + var(--tx)), calc(-50% + var(--ty))) scale(0);
        opacity: 0;
    }
}

@keyframes sparkle-star {
    0% {
        transform: translate(-50%, -50%) scale(0);
        opacity: 1;
    }
    30% {
        transform: translate(-50%, -50%) scale(1);
        opacity: 1;
    }
    100% {
        transform: translate(calc(-50% + var(--tx)), calc(-50% + var(--ty))) scale(0.2);
        opacity: 0;
    }
}

/* Wrong solution / game over animation */
.modal-wrong.modal-shake .modal-content {
    animation: wrongShake 0.6s ease-in-out;
}

.modal-wrong .modal-wrong-icon {
    animation: wrongPulse 0.5s ease-out;
}

@keyframes wrongShake {
    0%, 100% { transform: translateX(0); }
    15% { transform: translateX(-8px) rotate(-1deg); }
    30% { transform: translateX(8px) rotate(1deg); }
    45% { transform: translateX(-6px) rotate(-0.5deg); }
    60% { transform: translateX(6px) rotate(0.5deg); }
    75% { transform: translateX(-3px); }
}

@keyframes wrongPulse {
    0% { transform: scale(1); opacity: 1; }
    50% { transform: scale(1.15); opacity: 0.9; }
    100% { transform: scale(1); opacity: 1; }
}

/* Win trophy bounce */
.win-trophy {
    animation: trophyBounce 0.6s ease-out;
}

/* Win modal: visible "New Game" button */
.btn-win-new-game {
    background: linear-gradient(135deg, #00ba7c, #00d68f);
    color: #fff !important;
    border: none;
    border-radius: 10px;
    font-weight: 600;
    padding: 0.5rem 1.25rem;
    text-decoration: none;
    display: inline-block;
    transition: transform 0.2s, box-shadow 0.2s;
}

.btn-win-new-game:hover {
    color: #fff !important;
    background: linear-gradient(135deg, #00a36e, #00ba7c);
    transform: translateY(-1px);
    box-shadow: 0 4px 16px rgba(0, 186, 124, 0.4);
}

@keyframes trophyBounce {
    0% { transform: scale(0); opacity: 0; }
    50% { transform: scale(1.2); }
    70% { transform: scale(0.95); }
    100% { transform: scale(1); opacity: 1; }
}

/* ===== Animations ===== */
@keyframes shake {
    0%, 100% { transform: translateX(0); }
    20% { transform: translateX(-4px); }
    40% { transform: translateX(4px); }
    60% { transform: translateX(-2px); }
    80% { transform: translateX(2px); }
}

.cell.fill-in {
    animation: fillIn 0.3s ease;
}

@keyframes fillIn {
    0% { transform: scale(1.2); opacity: 0.7; }
    100% { transform: scale(1); opacity: 1; }
}

/* ===== How to Play page ===== */
.how-to-play-page main {
    max-width: 900px;
    margin-left: auto;
    margin-right: auto;
}

.howto-hero {
    padding: 2rem 1rem;
}

.howto-hero-icon {
    width: 4rem;
    height: 4rem;
    margin-left: auto;
    margin-right: auto;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-card);
    border: 1px solid var(--border-grid);
    border-radius: 50%;
    color: var(--accent);
    font-size: 1.75rem;
}

.howto-hero .display-5 {
    font-size: clamp(1.65rem, 2.5vw + 1rem, 2.5rem);
    line-height: 1.2;
    letter-spacing: -0.02em;
}

.content-narrow {
    max-width: 560px;
    margin-left: auto;
    margin-right: auto;
}

.content-panel,
.game-level-info,
.printable-info-panel {
    background: var(--bg-card);
    border: 1px solid var(--border-grid);
    border-radius: 12px;
    padding: 1rem 1.15rem;
}

.printable-info-panel {
    max-width: 640px;
    margin-left: auto;
    margin-right: auto;
}

.legal-summary {
    background: var(--bg-card);
    border: 1px solid var(--border-grid);
    border-radius: 12px;
    padding: 1rem 1.25rem;
}

.howto-card {
    background: var(--bg-card);
    border: 1px solid var(--border-grid);
    border-radius: 16px;
    overflow: hidden;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.15);
}

.howto-card-header {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1.25rem 1.5rem;
    border-bottom: 1px solid var(--border-grid);
}

.howto-card-icon {
    width: 3rem;
    height: 3rem;
    flex-shrink: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 12px;
    font-size: 1.25rem;
    color: #fff;
}

.howto-card-icon--goal { background: linear-gradient(135deg, #1d9bf0, #4db8f5); }
.howto-card-icon--rules { background: linear-gradient(135deg, #6366f1, #818cf8); }
.howto-card-icon--diff { background: linear-gradient(135deg, #8b5cf6, #a78bfa); }
.howto-card-icon--controls { background: linear-gradient(135deg, #0ea5e9, #38bdf8); }
.howto-card-icon--stats { background: linear-gradient(135deg, #64748b, #94a3b8); }

.howto-card-title {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
    margin: 0;
}

.howto-card-body {
    padding: 1.5rem;
}

.howto-card-text {
    color: var(--text-muted);
    margin-bottom: 0.5rem;
}

.howto-card-caption {
    color: var(--text-muted);
}

.howto-list {
    list-style: none;
    padding: 0;
    margin: 0;
    color: var(--text-muted);
}

.howto-list li {
    display: flex;
    align-items: flex-start;
    gap: 0.75rem;
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--border-grid);
}

.howto-list li:last-child {
    border-bottom: none;
}

.howto-list-icon {
    color: var(--accent);
    margin-top: 0.2rem;
    flex-shrink: 0;
    width: 1.25rem;
    text-align: center;
}

.howto-mini-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 4px;
    max-width: 120px;
}

.howto-mini-cell {
    aspect-ratio: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-cell);
    border: 1px solid var(--border-grid);
    border-radius: 6px;
    font-size: 0.9rem;
    font-weight: 700;
    color: var(--text-primary);
}

.howto-diff-badge {
    padding: 1rem 0.75rem;
    border-radius: 12px;
    text-align: center;
    color: #fff;
    transition: transform 0.2s, box-shadow 0.2s;
}

.howto-diff-badge:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 16px rgba(0, 0, 0, 0.2);
}

.howto-diff-easy { background: linear-gradient(135deg, #00ba7c, #00d68f); }
.howto-diff-medium { background: linear-gradient(135deg, #1d9bf0, #4db8f5); }
.howto-diff-hard { background: linear-gradient(135deg, #f59e0b, #fbbf24); color: #1a1a1a; }
.howto-diff-expert { background: linear-gradient(135deg, #ef4444, #f87171); }

.howto-control-item,
.howto-stat-item {
    display: flex;
    align-items: flex-start;
    gap: 1rem;
    padding: 1rem;
    background: var(--bg-cell);
    border: 1px solid var(--border-grid);
    border-radius: 12px;
}

.howto-control-icon {
    width: 2.75rem;
    height: 2.75rem;
    flex-shrink: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    background: rgba(29, 155, 240, 0.2);
    color: var(--accent);
    border-radius: 10px;
    font-size: 1.1rem;
}

.howto-stat-icon {
    width: 2.75rem;
    height: 2.75rem;
    flex-shrink: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-cell-hover);
    color: var(--accent);
    border-radius: 10px;
    font-size: 1.1rem;
}

.howto-stat-icon--mistakes {
    background: rgba(244, 33, 46, 0.15);
    color: var(--error);
}

.btn-howto-cta {
    background: linear-gradient(135deg, #00ba7c, #00d68f);
    color: #fff !important;
    border: none;
    border-radius: 14px;
    font-weight: 700;
    transition: transform 0.2s, box-shadow 0.2s;
}

.btn-howto-cta:hover {
    color: #fff !important;
    transform: translateY(-2px);
    box-shadow: 0 8px 24px rgba(0, 186, 124, 0.4);
}

/* FAQ / How to Play: Play Sudoku CTA – visible in light and dark theme */
.btn-play-cta {
    background: linear-gradient(135deg, #1d9bf0, #4db8f5);
    color: #fff !important;
    border: none;
    border-radius: 14px;
    font-weight: 700;
    transition: transform 0.2s, box-shadow 0.2s;
}

.btn-play-cta:hover {
    color: #fff !important;
    background: linear-gradient(135deg, #1a8cd8, #1d9bf0);
    transform: translateY(-2px);
    box-shadow: 0 8px 24px rgba(29, 155, 240, 0.4);
}

/* ===== FAQ accordion ===== */
.accordion-faq .accordion-item {
    background: var(--bg-card);
    border: 1px solid var(--border-grid);
    border-radius: 10px !important;
    margin-bottom: 0.75rem;
    overflow: hidden;
}

.accordion-faq .accordion-item:last-child {
    margin-bottom: 0;
}

.accordion-faq .accordion-button {
    background: var(--bg-card);
    color: var(--text-primary);
    font-weight: 600;
    border: none;
    box-shadow: none;
    padding: 1rem 1.25rem;
}

.accordion-faq .accordion-button:not(.collapsed) {
    background: var(--bg-cell-hover);
    color: var(--accent);
}

.accordion-faq .accordion-button:hover {
    background: var(--bg-cell-hover);
    color: var(--accent);
}

.accordion-faq .accordion-button::after {
    filter: invert(0.7);
}

[data-theme="light"] .accordion-faq .accordion-button::after {
    filter: none;
}

.accordion-faq .accordion-body {
    background: var(--bg-card);
    color: var(--text-muted);
    padding: 1rem 1.25rem 1.25rem;
    border-top: 1px solid var(--border-grid);
}

.faq-mini {
    flex: 1;
    min-width: 160px;
    padding: 0.75rem 1rem;
    background: var(--bg-card);
    border-radius: 10px;
    border: 1px solid var(--border-grid);
}

/* ===== Challenges calendar ===== */
.challenges-card,
.challenges-play-card {
    padding: 1.25rem 1.5rem;
}

.challenges-card-head {
    margin-bottom: 0.5rem;
}

.btn-challenges-nav {
    width: 2.25rem;
    height: 2.25rem;
    padding: 0;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    border-radius: 10px;
    background: rgba(29, 155, 240, 0.12);
    border: 1px solid rgba(29, 155, 240, 0.35);
    color: var(--accent);
    transition: background 0.15s, border-color 0.15s;
}

.btn-challenges-nav:hover:not(.disabled) {
    background: rgba(29, 155, 240, 0.22);
    border-color: var(--accent);
    color: var(--accent-hover);
}

.btn-challenges-nav.disabled {
    opacity: 0.35;
    pointer-events: none;
}

[data-theme="light"] .btn-challenges-nav {
    background: rgba(14, 165, 233, 0.1);
    border-color: rgba(14, 165, 233, 0.35);
}

.challenges-archive-note {
    line-height: 1.5;
}

.challenges-weekdays {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    gap: 4px;
    margin-bottom: 6px;
    text-align: center;
    font-size: 0.7rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.04em;
    color: var(--text-muted);
}

.challenges-grid {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    gap: 6px;
}

.challenges-cell {
    min-height: 3.35rem;
    border-radius: 12px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    position: relative;
    text-decoration: none;
    transition: transform 0.12s ease, box-shadow 0.12s ease, border-color 0.12s;
}

.challenges-cell--pad {
    background: transparent;
    border: none;
    pointer-events: none;
    min-height: 3.35rem;
}

.challenges-cell--day {
    background: var(--bg-cell);
    border: 1px solid var(--border-grid);
    color: var(--text-primary);
}

.challenges-cell--day:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 18px rgba(0, 0, 0, 0.2);
    border-color: var(--accent);
}

.challenges-cell--selected {
    border-color: var(--accent);
    box-shadow: 0 0 0 2px rgba(29, 155, 240, 0.35);
    background: rgba(29, 155, 240, 0.12);
}

[data-theme="light"] .challenges-cell--selected {
    box-shadow: 0 0 0 2px rgba(14, 165, 233, 0.35);
    background: rgba(14, 165, 233, 0.1);
}

.challenges-cell--selected-muted {
    border-color: var(--accent);
    box-shadow: 0 0 0 2px rgba(29, 155, 240, 0.22);
    opacity: 0.92;
}

.challenges-cell--selected-muted:hover {
    opacity: 1;
    border-color: var(--accent-hover);
}

[data-theme="light"] .challenges-cell--selected-muted {
    box-shadow: 0 0 0 2px rgba(14, 165, 233, 0.22);
}

.challenges-day-num {
    font-weight: 700;
    font-size: 1.05rem;
    line-height: 1;
}

.challenges-day-dots {
    display: flex;
    gap: 3px;
    margin-top: 5px;
}

.challenges-day-dots span {
    width: 4px;
    height: 4px;
    border-radius: 50%;
    background: var(--accent);
    opacity: 0.55;
}

.challenges-today-badge {
    position: absolute;
    top: 4px;
    right: 4px;
    font-size: 0.55rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.03em;
    color: var(--success);
    line-height: 1;
}

.challenges-cell--muted {
    background: rgba(139, 152, 165, 0.08);
    border: 1px dashed var(--border-grid);
    color: var(--text-muted);
    opacity: 0.65;
}

.challenges-cell--future {
    opacity: 0.45;
}

.challenges-play-card {
    border: 1px solid var(--border-grid);
}

.challenges-selected-label {
    font-weight: 600;
    letter-spacing: 0.02em;
}

.btn-challenges-play {
    display: flex;
    align-items: center;
    justify-content: space-between;
    text-align: left;
    padding: 0.75rem 1rem;
    border-radius: 12px;
    background: linear-gradient(135deg, rgba(29, 155, 240, 0.2) 0%, rgba(29, 155, 240, 0.06) 100%);
    border: 1px solid rgba(29, 155, 240, 0.45);
    color: var(--text-primary);
    font-weight: 600;
}

.btn-challenges-play:hover {
    background: linear-gradient(135deg, rgba(29, 155, 240, 0.35) 0%, rgba(29, 155, 240, 0.12) 100%);
    border-color: var(--accent);
    color: var(--text-primary);
}

[data-theme="light"] .btn-challenges-play {
    background: linear-gradient(135deg, rgba(14, 165, 233, 0.18) 0%, rgba(14, 165, 233, 0.06) 100%);
    border-color: rgba(14, 165, 233, 0.45);
}

.challenges-play-action {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--accent);
}

.challenge-context-banner {
    max-width: 520px;
    margin-left: auto;
    margin-right: auto;
    background: var(--bg-card);
    border: 1px solid rgba(29, 155, 240, 0.35);
    font-size: 0.9rem;
    /* Above play shells whose .row uses z-index: 1 (word search / magic square / crossword) */
    position: relative;
    z-index: 3;
    isolation: isolate;
}

.challenge-context-banner a {
    position: relative;
    z-index: 1;
}

[data-theme="light"] .challenge-context-banner {
    border-color: rgba(14, 165, 233, 0.4);
}

/* ===== Responsive ===== */
@media (max-width: 520px) {
    .numpad {
        grid-template-columns: repeat(5, 1fr);
    }
    .numpad-btn:nth-child(n+6) {
        grid-column: span 1;
    }
    .actions-bar {
        gap: 0.5rem;
    }
    .btn-action span {
        display: none;
    }
}

@media (max-width: 768px) {
    .howto-card-header {
        padding: 1rem 1.25rem;
    }
    .howto-card-body {
        padding: 1.25rem;
    }
}