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

:root {
    --primary-color: rgb(240, 240, 240);
    --secondary-color: rgb(200, 200, 200);
    --accent-color: rgb(160, 160, 160);
    --selection-color: rgb(255, 100, 0);
    --shadow-color: rgb(80, 80, 80);

    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;

    --container-max-width: 600px;
    --card-size: clamp(40px, 12vw, 80px);
}

body {
    display: flex;
    flex-direction: column;
    align-items: center;
    min-height: 100vh;
    padding: var(--spacing-md);
    font-family: 'Segoe UI', system-ui, sans-serif;
    font-size: 1rem;
    line-height: 1.5;
    background-color: var(--secondary-color);
}

.main {
    display: flex;
    flex-direction: column;
    align-items: center;
    width: 100%;
    max-width: var(--container-max-width);
    gap: var(--spacing-md);
}

.card {
    width: 100%;
    padding: var(--spacing-lg);
    background-color: var(--primary-color);
    box-shadow: 8px 8px 0 var(--shadow-color);
}

.btn {
    padding: var(--spacing-sm) var(--spacing-md);
    font-family: inherit;
    font-size: 1rem;
    font-weight: 600;
    color: inherit;
    background-color: var(--primary-color);
    border: 2px solid var(--shadow-color);
    border-radius: 0;
    box-shadow: 4px 4px 0 var(--shadow-color);
    outline: none;
    cursor: pointer;
    transition: transform 0.1s, box-shadow 0.1s;
    -webkit-appearance: none;
    appearance: none;
}

.btn:hover {
    background-color: var(--secondary-color);
}

.btn:focus {
    border-color: var(--selection-color);
}

.btn:active {
    border-color: var(--selection-color);
    box-shadow: 2px 2px 0 var(--shadow-color);
    transform: translate(2px, 2px);
}

.button-group {
    display: flex;
    flex-wrap: wrap;
    width: 100%;
    gap: var(--spacing-sm);
}

.button-group .btn {
    flex: 1 1 auto;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xs);
}

label {
    font-weight: 600;
}

select {
    padding: var(--spacing-sm);
    padding-right: 2.5rem;
    font-family: inherit;
    font-size: 1rem;
    color: inherit;
    background-color: var(--primary-color);
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' viewBox='0 0 24 24' fill='none' stroke='%233c3c3c' stroke-width='2'%3E%3Cpath d='M6 9l6 6 6-6'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right var(--spacing-sm) center;
    border: 2px solid var(--shadow-color);
    border-radius: 0;
    box-shadow: 4px 4px 0 var(--shadow-color);
    outline: none;
    cursor: pointer;
    -webkit-appearance: none;
    appearance: none;
}

select:focus {
    border-color: var(--selection-color);
}

.header {
    text-align: center;
}

.header h1 {
    margin: 0;
    font-size: clamp(1.5rem, 5vw, 2rem);
}

.settings {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-md);
}

.settings .form-group {
    flex: 1 1 200px;
}

.settings .btn {
    width: 100%;
}

.results {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.results__empty {
    text-align: center;
    color: var(--shadow-color);
}

.results__mode h3 {
    margin-bottom: var(--spacing-sm);
    font-size: 1.1rem;
}

.results__table {
    width: 100%;
    border-collapse: collapse;
}

.results__table th,
.results__table td {
    padding: var(--spacing-xs) var(--spacing-sm);
    text-align: left;
    border-bottom: 1px solid var(--accent-color);
}

.results__table th {
    font-weight: 600;
}

.game {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.game__stats {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: var(--spacing-sm) var(--spacing-md);
}

.game__cards {
    display: grid;
    justify-content: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-md) 0;
}

.game__cards.easy {
    grid-template-columns: repeat(4, var(--card-size));
}

.game__cards.medium {
    grid-template-columns: repeat(4, var(--card-size));
}

.game__cards.hard {
    grid-template-columns: repeat(6, var(--card-size));
}

.stat {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
}

.stat__label {
    font-weight: 600;
}

.stat__value {
    font-size: 1.1rem;
    font-weight: 700;
    font-variant-numeric: tabular-nums;
    color: var(--selection-color);
}

.flip-card {
    width: var(--card-size);
    height: var(--card-size);
    cursor: pointer;
    perspective: 1000px;
}

.flip-card-inner {
    position: relative;
    width: 100%;
    height: 100%;
    transition: transform 0.5s;
    transform-style: preserve-3d;
}

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

.flip-card-front,
.flip-card-back {
    position: absolute;
    display: flex;
    justify-content: center;
    align-items: center;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
}

.flip-card-front {
    background-color: var(--accent-color);
}

.flip-card-back {
    font-size: 2rem;
    background-color: var(--selection-color);
    transform: rotateY(180deg);
}

.flip-card.matched .flip-card-back {
    background-color: var(--secondary-color);
}

.modal {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-md);
    text-align: center;
}

.modal__message {
    font-size: clamp(1.25rem, 4vw, 1.5rem);
}

.modal__current-result,
.modal__best-result {
    font-size: 1rem;
    color: var(--shadow-color);
}

.modal__best-result {
    font-weight: 600;
    color: var(--selection-color);
}

.hidden {
    display: none !important;
}