:root {
    --bg: #050914;
    --panel: #0f172a;
    --panel-light: #1e293b;
    --text: #f8fafc;
    --muted: #94a3b8;
    --accent: #f59e0b;
    --danger: #ef4444;
}

* {
    box-sizing: border-box;
}

body {
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
    min-height: 100vh;
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
    color: var(--text);
    background: radial-gradient(circle at top, #1e1b4b, #020617 65%);
}

.calculator {
    width: min(960px, 100%);
    background: var(--panel);
    border-radius: 18px;
    padding: 28px;
    box-shadow: 0 25px 60px rgba(5, 10, 35, 0.55);
    display: flex;
    flex-direction: column;
    gap: 18px;
}

header h1 {
    margin: 0;
    font-size: clamp(1.4rem, 2.2vw, 1.8rem);
}

header p {
    margin: 4px 0 0;
    color: var(--muted);
    font-size: 0.95rem;
}

.display-wrapper {
    background: var(--panel-light);
    border-radius: 12px;
    padding: 16px;
    box-shadow: inset 0 0 0 1px rgba(148, 163, 184, 0.1);
}

#display {
    width: 100%;
    border: none;
    background: transparent;
    color: var(--text);
    font-size: clamp(2rem, 4.4vw, 2.8rem);
    text-align: right;
    padding: 6px 0;
    letter-spacing: 1px;
}

#display:focus {
    outline: none;
}

#display.updated {
    text-shadow: 0 0 12px rgba(245, 158, 11, 0.75);
}

#status {
    min-height: 20px;
    font-size: 0.85rem;
    color: var(--muted);
}

.workspace {
    display: grid;
    grid-template-columns: 3fr 2fr;
    gap: 18px;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, minmax(60px, 1fr));
    gap: 12px;
}

.buttons button {
    border: none;
    border-radius: 12px;
    font-size: 1.1rem;
    font-weight: 500;
    background: rgba(255, 255, 255, 0.06);
    color: var(--text);
    cursor: pointer;
    transition: transform 0.08s ease, background 0.2s ease, box-shadow 0.2s ease;
}

.buttons button:hover {
    background: rgba(255, 255, 255, 0.12);
}

.buttons button:active {
    transform: scale(0.95);
}

.buttons button:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

.buttons .accent {
    background: rgba(245, 158, 11, 0.15);
    color: #fed7aa;
}

.buttons .accent:hover {
    background: rgba(245, 158, 11, 0.25);
}

.buttons .equals {
    grid-column: span 2;
    background: linear-gradient(120deg, #f97316, #facc15);
    color: #0f172a;
    font-weight: 700;
}

.history {
    background: var(--panel-light);
    border-radius: 12px;
    padding: 16px;
    display: flex;
    flex-direction: column;
    gap: 12px;
    box-shadow: inset 0 0 0 1px rgba(148, 163, 184, 0.12);
}

.history-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.history-header h2 {
    margin: 0;
    font-size: 1.1rem;
}

.link-button {
    border: none;
    background: none;
    color: var(--muted);
    font-size: 0.85rem;
    cursor: pointer;
    text-decoration: underline;
}

.link-button:hover {
    color: var(--text);
}

#history-list {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    flex-direction: column;
    gap: 10px;
    max-height: 260px;
    overflow-y: auto;
}

#history-list li {
    background: rgba(0, 0, 0, 0.15);
    border-radius: 10px;
    padding: 10px 12px;
    font-size: 0.95rem;
    display: flex;
    justify-content: space-between;
    gap: 12px;
}

#history-list li span {
    color: var(--muted);
}

@media (max-width: 900px) {
    .workspace {
        grid-template-columns: 1fr;
    }

    .history {
        order: -1;
    }
}

@media (max-width: 520px) {
    body {
        padding: 12px;
    }

    .calculator {
        padding: 18px;
    }

    .buttons {
        grid-template-columns: repeat(4, minmax(0, 1fr));
    }

    .buttons button {
        font-size: 1rem;
    }
}