/* Tile flip — sketch / notebook paper theme */
:root {
    --paper: #f4efe4;
    --paper-shadow: #dcd3c4;
    --ink: #2b2724;
    --pencil: #4a433c;
    --pencil-light: #7a7268;
    --card-back: #e0d5c4;
    --card-front: #fffdf7;
    --line-blue: rgba(58, 107, 165, 0.22);
    --match-ink: #3d5c40;
    --match-bg: #d4e8d6;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html,
body {
    height: 100%;
    font-family: 'Patrick Hand', 'Segoe Print', 'Bradley Hand', cursive;
    color: var(--ink);
    overflow: hidden;
    background-color: var(--paper);
    /* Subtle notebook paper + margin line */
    background-image:
        linear-gradient(90deg, transparent 0 47px, var(--line-blue) 47px 48px, transparent 48px),
        repeating-linear-gradient(
            transparent,
            transparent 27px,
            rgba(74, 67, 60, 0.06) 27px,
            rgba(74, 67, 60, 0.06) 28px
        ),
        radial-gradient(ellipse 120% 80% at 50% -20%, rgba(255, 255, 255, 0.35), transparent 55%);
    background-size: 100% 100%, 100% 28px, 100% 100%;
}

.app {
    display: flex;
    flex-direction: column;
    height: 100%;
    max-width: 720px;
    margin: 0 auto;
    padding: 14px 18px 22px 56px;
}

header {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    margin-bottom: 16px;
    flex-shrink: 0;
}

.stats {
    display: flex;
    gap: 20px;
    font-size: 1.15rem;
    color: var(--pencil);
    letter-spacing: 0.02em;
}

.stats strong {
    color: var(--ink);
    font-variant-numeric: tabular-nums;
    font-family: 'Caveat', cursive;
    font-size: 1.35rem;
    font-weight: 700;
}

/* Hand-drawn-ish button */
.btn {
    appearance: none;
    font-family: 'Patrick Hand', cursive;
    border: 2px solid var(--ink);
    color: var(--ink);
    padding: 8px 18px;
    font-size: 1.1rem;
    cursor: pointer;
    background: var(--card-front);
    border-radius: 255px 12px 225px 12px / 12px 225px 12px 255px;
    box-shadow: 3px 4px 0 rgba(43, 39, 36, 0.12);
    transition: transform 0.12s ease, box-shadow 0.12s ease, background 0.15s ease;
}

.btn:hover {
    background: #fff;
    box-shadow: 4px 5px 0 rgba(43, 39, 36, 0.15);
}

.btn:active {
    transform: translate(1px, 2px);
    box-shadow: 1px 2px 0 rgba(43, 39, 36, 0.12);
}

.btn:focus-visible {
    outline: 2px dashed var(--pencil-light);
    outline-offset: 3px;
}

.board-wrap {
    flex: 1;
    min-height: 0;
    display: flex;
    align-items: center;
    justify-content: center;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 10px;
    flex-wrap: wrap;
}

.diff-group {
    display: flex;
    gap: 6px;
}

.btn-diff {
    padding: 6px 14px;
    font-size: 1rem;
}

.btn-diff-active {
    background: var(--card-back);
    box-shadow: inset 0 0 0 2px var(--ink), 2px 3px 0 rgba(43, 39, 36, 0.1);
}

.board {
    display: grid;
    grid-template-columns: repeat(var(--cols, 4), 1fr);
    grid-template-rows: repeat(var(--rows, 4), 1fr);
    gap: clamp(6px, 2vw, 12px);
    width: var(--board-w, min(92vw, 400px));
    aspect-ratio: var(--cols, 4) / var(--rows, 4);
    margin: 0 auto;
    padding: 10px;
    background: rgba(255, 253, 247, 0.65);
    border: 2px solid var(--ink);
    border-radius: 4px 12px 8px 10px / 10px 6px 12px 8px;
    box-shadow: 4px 5px 0 rgba(43, 39, 36, 0.08), inset 0 1px 0 rgba(255, 255, 255, 0.8);
}

.card {
    position: relative;
    perspective: 700px;
    cursor: pointer;
    border: none;
    background: transparent;
    padding: 0;
    border-radius: 6px 10px 8px 9px;
    -webkit-tap-highlight-color: transparent;
}

.card:disabled {
    cursor: default;
}

.card-inner {
    display: block;
    position: relative;
    width: 100%;
    height: 100%;
    border-radius: 6px 10px 8px 9px;
    transition: transform 0.5s cubic-bezier(0.4, 0, 0.2, 1);
    transform-style: preserve-3d;
    box-shadow: 2px 3px 0 rgba(43, 39, 36, 0.15);
}

.card.flipped .card-inner,
.card.matched .card-inner {
    transform: rotateY(180deg);
}

.card-face {
    position: absolute;
    inset: 0;
    border-radius: 6px 10px 8px 9px;
    display: flex;
    align-items: center;
    justify-content: center;
    backface-visibility: hidden;
    -webkit-backface-visibility: hidden;
    border: 2px solid var(--ink);
}

.card-back {
    background-color: var(--card-back);
    background-image:
        repeating-linear-gradient(
            -12deg,
            transparent,
            transparent 4px,
            rgba(43, 39, 36, 0.04) 4px,
            rgba(43, 39, 36, 0.04) 5px
        ),
        linear-gradient(165deg, #ebe1d2 0%, #d4c9b8 100%);
}

.card-back::after {
    content: '?';
    font-family: 'Caveat', cursive;
    font-size: clamp(1.6rem, 7vw, 2.4rem);
    font-weight: 700;
    color: var(--pencil-light);
    transform: rotate(-8deg);
}

.card-front {
    transform: rotateY(180deg);
    background: var(--card-front);
    background-image: radial-gradient(circle at 30% 20%, rgba(255, 255, 255, 0.9) 0%, transparent 45%);
    font-size: clamp(1.45rem, 7vw, 2.2rem);
    line-height: 1;
    box-shadow: inset 0 0 0 1px rgba(43, 39, 36, 0.06);
}

.card.matched .card-front {
    border-color: var(--match-ink);
    background: var(--match-bg);
    box-shadow: inset 0 0 0 2px rgba(61, 92, 64, 0.35);
}

.card:not(.matched):not(:disabled):hover .card-inner {
    box-shadow: 3px 5px 0 rgba(43, 39, 36, 0.2);
}

.overlay {
    position: fixed;
    inset: 0;
    background: rgba(43, 39, 36, 0.35);
    backdrop-filter: blur(2px);
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 24px;
    z-index: 50;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.25s ease;
}

.overlay.visible {
    opacity: 1;
    pointer-events: auto;
}

.dialog {
    background: var(--card-front);
    border: 3px solid var(--ink);
    border-radius: 8px 14px 10px 12px / 12px 8px 14px 10px;
    padding: 28px 32px;
    text-align: center;
    max-width: 320px;
    box-shadow: 6px 8px 0 rgba(43, 39, 36, 0.12), 0 0 0 1px rgba(43, 39, 36, 0.08) inset;
}

.dialog h2 {
    font-family: 'Caveat', cursive;
    font-size: 1.85rem;
    font-weight: 700;
    margin-bottom: 10px;
    color: var(--ink);
    line-height: 1.2;
}

.dialog p {
    color: var(--pencil);
    font-size: 1.15rem;
    margin-bottom: 22px;
}

.dialog p strong {
    font-family: 'Caveat', cursive;
    font-size: 1.4rem;
    color: var(--ink);
}