:root {
    --bg: #0b1020;
    --bg-2: #111834;
    --card: rgba(255, 255, 255, 0.05);
    --border: rgba(255, 255, 255, 0.12);
    --text: #e7ecf5;
    --muted: #9aa6c4;
    --accent: #7c5cff;
    --accent-2: #21d4fd;
    --glow: 0 0 24px rgba(124, 92, 255, 0.55);

    --calc-bg: rgba(15, 20, 40, 0.75);
    --calc-border: rgba(255, 255, 255, 0.10);
    --btn-bg: rgba(255, 255, 255, 0.06);
    --btn-bg-hover: rgba(255, 255, 255, 0.12);
    --btn-text: #e7ecf5;
    --operator-bg: linear-gradient(120deg, var(--accent), #5b8cff);
    --operator-text: #ffffff;
    --function-bg: rgba(255, 92, 168, 0.16);
    --function-text: #ff9ad1;
    --equals-bg: linear-gradient(120deg, var(--accent), var(--accent-2));
    --equals-text: #ffffff;
    --display-bg: rgba(0, 0, 0, 0.30);
    --history-text: var(--muted);
}

[data-theme="light"] {
    --bg: #eef1f8;
    --bg-2: #dfe6f7;
    --card: rgba(255, 255, 255, 0.7);
    --border: rgba(20, 30, 60, 0.12);
    --text: #1a2238;
    --muted: #5a678a;
    --accent: #6a44ff;
    --accent-2: #0fb6e6;
    --glow: 0 0 22px rgba(106, 68, 255, 0.30);

    --calc-bg: rgba(255, 255, 255, 0.85);
    --calc-border: rgba(20, 30, 60, 0.12);
    --btn-bg: rgba(255, 255, 255, 0.9);
    --btn-bg-hover: #ffffff;
    --btn-text: #1a2238;
    --operator-bg: linear-gradient(120deg, var(--accent), #517bff);
    --operator-text: #ffffff;
    --function-bg: rgba(255, 92, 168, 0.18);
    --function-text: #c4256e;
    --equals-bg: linear-gradient(120deg, var(--accent), var(--accent-2));
    --equals-text: #ffffff;
    --display-bg: rgba(20, 30, 60, 0.06);
    --history-text: var(--muted);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
    margin: 0;
    min-height: 100vh;
    font-family: 'Inter', system-ui, sans-serif;
    background: radial-gradient(1200px 800px at 70% -10%, var(--bg-2), var(--bg) 60%);
    color: var(--text);
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 24px;
    transition: background 0.4s ease, color 0.4s ease;
}

.bg-orbs { position: fixed; inset: 0; z-index: 0; pointer-events: none; overflow: hidden; }
.orb {
    position: absolute;
    border-radius: 50%;
    opacity: 0.40;
    transform: translateZ(0);
    animation: float 16s ease-in-out infinite;
}
.orb-1 { width: 420px; height: 420px; background: radial-gradient(circle at 50% 50%, var(--accent) 0%, transparent 70%); top: -120px; left: -80px; }
.orb-2 { width: 360px; height: 360px; background: radial-gradient(circle at 50% 50%, var(--accent-2) 0%, transparent 70%); bottom: -100px; right: -60px; animation-delay: -5s; }
.orb-3 { width: 300px; height: 300px; background: radial-gradient(circle at 50% 50%, #ff5ca8 0%, transparent 70%); top: 40%; left: 55%; animation-delay: -9s; }

@keyframes float {
    0%, 100% { transform: translate(0, 0) scale(1); }
    50% { transform: translate(30px, -40px) scale(1.08); }
}

.calculator {
    position: relative;
    z-index: 1;
    width: 100%;
    max-width: 360px;
    padding: 22px;
    border-radius: 26px;
    background: var(--calc-bg);
    border: 1px solid var(--calc-border);
    box-shadow: 0 24px 60px rgba(0, 0, 0, 0.45), var(--glow);
    backdrop-filter: blur(14px);
    -webkit-backdrop-filter: blur(14px);
    animation: pop 0.6s ease both;
}

@keyframes pop {
    0% { transform: scale(0.92) translateY(14px); opacity: 0; }
    100% { transform: scale(1) translateY(0); opacity: 1; }
}

.calc-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 16px;
}

.brand { display: flex; align-items: center; gap: 10px; }
.brand-logo {
    width: 34px;
    height: 34px;
    border-radius: 9px;
    border: 1px solid var(--calc-border);
    object-fit: cover;
    box-shadow: var(--glow);
    background: var(--btn-bg);
}
.brand-name {
    font-family: 'Space Grotesk', sans-serif;
    font-weight: 700;
    font-size: 1.15rem;
    letter-spacing: 0.3px;
}

.theme-toggle {
    width: 40px;
    height: 40px;
    border-radius: 12px;
    border: 1px solid var(--calc-border);
    background: var(--btn-bg);
    color: var(--text);
    font-size: 1.2rem;
    line-height: 1;
    cursor: pointer;
    display: grid;
    place-items: center;
    transition: transform 0.2s, border-color 0.2s, box-shadow 0.2s;
}
.theme-toggle:hover { transform: translateY(-2px); border-color: var(--accent); box-shadow: var(--glow); }

.display {
    border-radius: 16px;
    background: var(--display-bg);
    border: 1px solid var(--calc-border);
    padding: 14px 16px;
    margin-bottom: 16px;
    text-align: right;
    overflow: hidden;
}
.history {
    min-height: 18px;
    font-size: 0.85rem;
    color: var(--history-text);
    margin-bottom: 4px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}
#display {
    width: 100%;
    border: none;
    background: transparent;
    color: var(--text);
    font-family: 'Space Grotesk', sans-serif;
    font-size: clamp(1.6rem, 8vw, 2.2rem);
    font-weight: 600;
    text-align: right;
    outline: none;
    letter-spacing: 0.5px;
}

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

.buttons button {
    border: 1px solid var(--calc-border);
    background: var(--btn-bg);
    color: var(--btn-text);
    font-family: 'Space Grotesk', sans-serif;
    font-size: 1.25rem;
    font-weight: 600;
    padding: 16px 0;
    border-radius: 14px;
    cursor: pointer;
    user-select: none;
    transition: transform 0.12s ease, background 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}
.buttons button:hover { background: var(--btn-bg-hover); transform: translateY(-2px); }
.buttons button:active { transform: translateY(0) scale(0.96); }

.buttons .function {
    background: var(--function-bg);
    color: var(--function-text);
    border-color: transparent;
}
.buttons .operator {
    background: var(--operator-bg);
    color: var(--operator-text);
    border-color: transparent;
}
.buttons .equals {
    background: var(--equals-bg);
    color: var(--equals-text);
    border-color: transparent;
    box-shadow: var(--glow);
}
.buttons .zero { font-weight: 700; }

.buttons button.flash { animation: flash 0.18s ease; }
@keyframes flash {
    0% { transform: scale(1); }
    50% { transform: scale(0.93); }
    100% { transform: scale(1); }
}

.hint {
    margin: 16px 2px 0;
    font-size: 0.72rem;
    color: var(--muted);
    text-align: center;
    line-height: 1.5;
}
.hint kbd {
    background: var(--btn-bg);
    border: 1px solid var(--calc-border);
    border-radius: 5px;
    padding: 1px 5px;
    font-family: 'Inter', sans-serif;
    font-size: 0.68rem;
}

@media (prefers-reduced-motion: reduce) {
    .orb, .calculator { animation: none; }
    .buttons button { transition: none; }
}