/* ---------- Theme tokens ---------- */

:root {
    color-scheme: light;

    --bg-1: #f0fdf4;
    --bg-2: #e2e8f0;
    --card: #ffffff;
    --card-border: rgba(15, 23, 42, 0.06);
    --shadow: 0 24px 60px -16px rgba(15, 23, 42, 0.28), 0 4px 14px rgba(15, 23, 42, 0.06);
    --text: #0f172a;
    --muted: #64748b;
    --display: #f8fafc;

    --key: #f1f5f9;
    --key-hover: #e2e8f0;
    --key-text: #0f172a;
    --function: #e2e8f0;
    --function-hover: #cbd5e1;
    --function-text: #334155;
    --operator: #dcfce7;
    --operator-hover: #bbf7d0;
    --operator-text: #166534;
    --equals: #15803D;
    --equals-hover: #166534;
    --equals-text: #ffffff;

    --focus: #15803D;
}

/* Dark: follows the system unless the user picked light */
@media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) {
        color-scheme: dark;

        --bg-1: #0b1220;
        --bg-2: #111827;
        --card: #1a1f2b;
        --card-border: rgba(255, 255, 255, 0.06);
        --shadow: 0 24px 60px -16px rgba(0, 0, 0, 0.7), 0 4px 14px rgba(0, 0, 0, 0.3);
        --text: #f1f5f9;
        --muted: #94a3b8;
        --display: #141824;

        --key: #262c3a;
        --key-hover: #2f3647;
        --key-text: #f1f5f9;
        --function: #323a4c;
        --function-hover: #3b4459;
        --function-text: #e2e8f0;
        --operator: rgba(74, 222, 128, 0.14);
        --operator-hover: rgba(74, 222, 128, 0.22);
        --operator-text: #86efac;
        --equals: #22c55e;
        --equals-hover: #4ade80;
        --equals-text: #052e16;

        --focus: #4ade80;
    }
}

/* Dark: chosen with the toggle */
:root[data-theme="dark"] {
    color-scheme: dark;

    --bg-1: #0b1220;
    --bg-2: #111827;
    --card: #1a1f2b;
    --card-border: rgba(255, 255, 255, 0.06);
    --shadow: 0 24px 60px -16px rgba(0, 0, 0, 0.7), 0 4px 14px rgba(0, 0, 0, 0.3);
    --text: #f1f5f9;
    --muted: #94a3b8;
    --display: #141824;

    --key: #262c3a;
    --key-hover: #2f3647;
    --key-text: #f1f5f9;
    --function: #323a4c;
    --function-hover: #3b4459;
    --function-text: #e2e8f0;
    --operator: rgba(74, 222, 128, 0.14);
    --operator-hover: rgba(74, 222, 128, 0.22);
    --operator-text: #86efac;
    --equals: #22c55e;
    --equals-hover: #4ade80;
    --equals-text: #052e16;

    --focus: #4ade80;
}

/* ---------- Page ---------- */

* {
    box-sizing: border-box;
}

html, body {
    margin: 0;
}

body {
    min-height: 100vh;
    min-height: 100dvh;
    padding: 24px 16px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--bg-1) 0%, var(--bg-2) 100%);
    background-attachment: fixed;
    color: var(--text);
    font-family: Inter, system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    -webkit-font-smoothing: antialiased;
}

/* ---------- Card ---------- */

.calculator {
    width: 100%;
    max-width: 360px;
    padding: 20px;
    border-radius: 28px;
    background: var(--card);
    border: 1px solid var(--card-border);
    box-shadow: var(--shadow);
}

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

.title {
    margin: 0;
    font-size: 15px;
    font-weight: 600;
    letter-spacing: 0.02em;
    color: var(--muted);
}

.theme-toggle {
    width: 36px;
    height: 36px;
    display: grid;
    place-items: center;
    padding: 0;
    border: none;
    border-radius: 50%;
    background: var(--key);
    color: var(--text);
    cursor: pointer;
    transition: background-color 0.15s, transform 0.1s;
}

.theme-toggle:hover {
    background: var(--key-hover);
}

.theme-toggle:active {
    transform: scale(0.92);
}

.theme-toggle .icon-sun {
    display: none;
}

.theme-toggle.is-dark .icon-sun {
    display: block;
}

.theme-toggle.is-dark .icon-moon {
    display: none;
}

/* ---------- Display ---------- */

.display {
    min-height: 116px;
    margin-bottom: 16px;
    padding: 14px 18px;
    border-radius: 18px;
    background: var(--display);
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
    gap: 4px;
    font-variant-numeric: tabular-nums;
}

/* Right-aligned flex rows clip overflow on the left, so the newest digits stay visible */
.expression,
.result {
    display: flex;
    justify-content: flex-end;
    white-space: nowrap;
    overflow: hidden;
}

.expression {
    min-height: 1.4em;
    font-size: 16px;
    color: var(--muted);
}

.result-value {
    flex-shrink: 0;
    font-size: 48px; /* max size; calculator.js shrinks it to fit */
    font-weight: 600;
    line-height: 1.15;
    letter-spacing: -0.02em;
}

/* ---------- Keys ---------- */

.keys {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}

.key {
    height: clamp(52px, 8.5dvh, 64px);
    min-width: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 0;
    border: none;
    border-radius: 16px;
    background: var(--key);
    color: var(--key-text);
    font: inherit;
    font-size: 22px;
    font-weight: 600;
    cursor: pointer;
    user-select: none;
    -webkit-tap-highlight-color: transparent;
    transition: background-color 0.15s, transform 0.08s ease-out, box-shadow 0.15s;
}

.key:hover {
    background: var(--key-hover);
    transform: translateY(-1px);
}

.key:active,
.key.pressed {
    transform: scale(0.95);
}

.key.function {
    background: var(--function);
    color: var(--function-text);
}

.key.function:hover {
    background: var(--function-hover);
}

.key.operator {
    background: var(--operator);
    color: var(--operator-text);
    font-size: 26px;
}

.key.operator:hover {
    background: var(--operator-hover);
}

.key.equals {
    background: var(--equals);
    color: var(--equals-text);
    font-size: 26px;
    box-shadow: 0 6px 16px -6px var(--equals);
}

.key.equals:hover {
    background: var(--equals-hover);
}

.key:focus-visible,
.theme-toggle:focus-visible {
    outline: 3px solid var(--focus);
    outline-offset: 2px;
}

/* ---------- Responsive ---------- */

/* Phones in landscape: display on the left, keys on the right */
@media (orientation: landscape) and (max-height: 500px) {
    body {
        padding: 8px 16px;
    }

    .calculator {
        max-width: 640px;
        padding: 12px;
        display: grid;
        grid-template-columns: 1fr 1.3fr;
        grid-template-rows: auto 1fr;
        column-gap: 14px;
    }

    .calculator-header {
        grid-column: 1;
        grid-row: 1;
    }

    .display {
        grid-column: 1;
        grid-row: 2;
        min-height: 0;
        margin-bottom: 0;
    }

    .keys {
        grid-column: 2;
        grid-row: 1 / 3;
        gap: 6px;
    }

    .key {
        height: clamp(36px, calc((100dvh - 64px) / 5), 56px);
        border-radius: 12px;
    }

    .result-value {
        font-size: 40px;
    }
}

/* Very narrow phones */
@media (max-width: 340px) {
    .calculator {
        padding: 14px;
        border-radius: 22px;
    }

    .keys {
        gap: 8px;
    }
}

@media (prefers-reduced-motion: reduce) {
    .key,
    .theme-toggle {
        transition: none;
    }

    .key:hover {
        transform: none;
    }
}