/* ===== Reset & Base ===== */
*,
*::before,
*::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --bg-dark: #0a0e1a;
    --card-bg: rgba(255, 255, 255, 0.06);
    --card-border: rgba(255, 255, 255, 0.12);
    --accent: #6c63ff;
    --accent-glow: rgba(108, 99, 255, 0.4);
    --accent-2: #f857a6;
    --accent-2-glow: rgba(248, 87, 166, 0.35);
    --text: #e8e6f0;
    --text-dim: #9996b0;
    --success: #34d399;
    --warning: #fbbf24;
    --danger: #f87171;
    --radius: 16px;
    --font: system-ui, -apple-system, 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', sans-serif;
}

html {
    font-size: 16px;
}

body {
    font-family: var(--font);
    background: var(--bg-dark);
    color: var(--text);
    min-height: 100vh;
    overflow-x: hidden;
    display: flex;
    justify-content: center;
    padding: 2rem 1rem;
}

/* ===== Animated Background Orbs ===== */
.bg-orbs {
    position: fixed;
    inset: 0;
    z-index: 0;
    pointer-events: none;
    overflow: hidden;
}

.orb {
    position: absolute;
    border-radius: 50%;
    filter: blur(100px);
    opacity: 0.5;
    animation: float 18s ease-in-out infinite;
}

.orb-1 {
    width: 500px;
    height: 500px;
    background: radial-gradient(circle, var(--accent) 0%, transparent 70%);
    top: -10%;
    left: -10%;
    animation-delay: 0s;
}

.orb-2 {
    width: 400px;
    height: 400px;
    background: radial-gradient(circle, var(--accent-2) 0%, transparent 70%);
    bottom: -10%;
    right: -10%;
    animation-delay: -6s;
}

.orb-3 {
    width: 300px;
    height: 300px;
    background: radial-gradient(circle, #38bdf8 0%, transparent 70%);
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    animation-delay: -12s;
}

@keyframes float {

    0%,
    100% {
        transform: translate(0, 0) scale(1);
    }

    25% {
        transform: translate(60px, -40px) scale(1.1);
    }

    50% {
        transform: translate(-30px, 50px) scale(0.95);
    }

    75% {
        transform: translate(40px, 30px) scale(1.05);
    }
}

/* ===== Layout ===== */
.container {
    position: relative;
    z-index: 1;
    width: 100%;
    max-width: 600px;
}

/* ===== Header ===== */
.header {
    text-align: center;
    margin-bottom: 2rem;
}

.title {
    font-size: 2.6rem;
    font-weight: 900;
    background: linear-gradient(135deg, #6c63ff 0%, #f857a6 50%, #38bdf8 100%);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    line-height: 1.3;
}

.title-icon {
    -webkit-text-fill-color: initial;
    font-size: 2.2rem;
    animation: pulse-icon 2s ease-in-out infinite;
}

@keyframes pulse-icon {

    0%,
    100% {
        transform: scale(1);
    }

    50% {
        transform: scale(1.15);
    }
}

.subtitle {
    margin-top: 0.6rem;
    color: var(--text-dim);
    font-size: 1rem;
    line-height: 1.6;
}

.subtitle strong {
    color: var(--accent-2);
    font-weight: 700;
    font-size: 1.15em;
}

/* ===== Mode Switch ===== */
.mode-switch {
    display: inline-flex;
    gap: 0.35rem;
    margin-top: 1.2rem;
    padding: 0.3rem;
    border: 1px solid var(--card-border);
    border-radius: 99px;
    background: var(--card-bg);
}

.mode-link {
    padding: 0.55rem 1.1rem;
    border-radius: 99px;
    color: var(--text-dim);
    font-weight: 700;
    text-decoration: none;
    transition: background 0.2s, color 0.2s;
}

.mode-link:hover {
    color: var(--text);
    background: rgba(255, 255, 255, 0.08);
}

.mode-link[aria-current="page"] {
    color: #fff;
    background: linear-gradient(135deg, var(--accent), var(--accent-2));
    box-shadow: 0 2px 12px var(--accent-glow);
}

.mode-link:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 3px;
}

/* ===== Card ===== */
.card {
    background: var(--card-bg);
    backdrop-filter: blur(24px) saturate(1.4);
    -webkit-backdrop-filter: blur(24px) saturate(1.4);
    border: 1px solid var(--card-border);
    border-radius: var(--radius);
    padding: 1.8rem;
    margin-bottom: 1.4rem;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.card:hover {
    transform: translateY(-2px);
    box-shadow: 0 12px 40px rgba(0, 0, 0, 0.3);
}

/* ===== Number Inputs ===== */
.input-row {
    display: flex;
    gap: 0.75rem;
    justify-content: center;
    flex-wrap: nowrap;
}

.num-input-wrapper {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.4rem;
}

.num-input-wrapper label {
    font-size: 0.85rem;
    color: var(--text-dim);
    font-weight: 600;
}

.num-input {
    width: 68px;
    height: 68px;
    min-width: 0;
    border: 2px solid var(--card-border);
    border-radius: 14px;
    background: rgba(255, 255, 255, 0.04);
    color: var(--text);
    font-family: var(--font);
    font-size: 1.6rem;
    font-weight: 700;
    text-align: center;
    outline: none;
    transition: border-color 0.25s, box-shadow 0.25s, transform 0.2s;
    appearance: textfield;
    -moz-appearance: textfield;
}

.num-input::-webkit-inner-spin-button,
.num-input::-webkit-outer-spin-button {
    -webkit-appearance: none;
    margin: 0;
}

.num-input:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 4px var(--accent-glow);
    transform: scale(1.05);
}

.num-input.error {
    border-color: var(--danger);
    box-shadow: 0 0 0 4px rgba(248, 113, 113, 0.25);
    animation: shake 0.4s ease;
}

@keyframes shake {

    0%,
    100% {
        transform: translateX(0);
    }

    20% {
        transform: translateX(-6px);
    }

    40% {
        transform: translateX(6px);
    }

    60% {
        transform: translateX(-4px);
    }

    80% {
        transform: translateX(4px);
    }
}

/* ===== Buttons ===== */
.btn-row {
    display: flex;
    gap: 0.8rem;
    justify-content: center;
    margin-top: 1.5rem;
}

.btn {
    font-family: var(--font);
    font-size: 1rem;
    font-weight: 700;
    border: none;
    border-radius: 12px;
    padding: 0.8rem 1.8rem;
    cursor: pointer;
    transition: transform 0.2s, box-shadow 0.2s, opacity 0.2s;
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
}

.btn:active {
    transform: scale(0.96);
}

.btn-primary {
    background: linear-gradient(135deg, var(--accent), var(--accent-2));
    color: #fff;
    box-shadow: 0 4px 20px var(--accent-glow);
}

.btn-primary:hover {
    box-shadow: 0 6px 30px var(--accent-glow), 0 0 60px var(--accent-2-glow);
    transform: translateY(-2px);
}

.btn-primary:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none;
    box-shadow: none;
}

.btn-secondary {
    background: rgba(255, 255, 255, 0.08);
    color: var(--text);
    border: 1px solid var(--card-border);
}

.btn-secondary:hover {
    background: rgba(255, 255, 255, 0.14);
    transform: translateY(-2px);
}

/* ===== Results ===== */
.result-card {
    animation: slideUp 0.5s cubic-bezier(0.22, 1, 0.36, 1);
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.result-header {
    text-align: center;
    margin-bottom: 1.2rem;
}

.result-header .badge {
    display: inline-block;
    font-size: 0.85rem;
    font-weight: 700;
    padding: 0.35rem 1rem;
    border-radius: 99px;
    letter-spacing: 0.03em;
}

.badge-perfect {
    background: linear-gradient(135deg, rgba(52, 211, 153, 0.2), rgba(52, 211, 153, 0.1));
    color: var(--success);
    border: 1px solid rgba(52, 211, 153, 0.3);
}

.badge-close {
    background: linear-gradient(135deg, rgba(251, 191, 36, 0.2), rgba(251, 191, 36, 0.1));
    color: var(--warning);
    border: 1px solid rgba(251, 191, 36, 0.3);
}

.result-header .best-value {
    display: block;
    font-size: 3rem;
    font-weight: 900;
    margin-top: 0.5rem;
    background: linear-gradient(135deg, #6c63ff, #38bdf8);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.result-header .diff-info {
    font-size: 0.9rem;
    color: var(--text-dim);
    margin-top: 0.3rem;
}

.result-list {
    display: flex;
    flex-direction: column;
    gap: 0.6rem;
}


.result-item {
    background: rgba(255, 255, 255, 0.04);
    border: 1px solid rgba(255, 255, 255, 0.07);
    border-radius: 10px;
    padding: 0.8rem 1rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 0.8rem;
    transition: background 0.2s;
    animation: fadeIn 0.3s ease;
}

.result-item:hover {
    background: rgba(255, 255, 255, 0.08);
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateX(-8px);
    }

    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.result-expr {
    font-size: 1.05rem;
    font-weight: 600;
    color: var(--text);
    word-break: break-word;
    overflow-wrap: break-word;
    min-width: 0;
}

.result-val {
    font-size: 0.85rem;
    font-weight: 700;
    padding: 0.25rem 0.7rem;
    border-radius: 8px;
    white-space: nowrap;
    flex-shrink: 0;
}

.result-val-perfect {
    background: rgba(52, 211, 153, 0.15);
    color: var(--success);
}

.result-val-close {
    background: rgba(251, 191, 36, 0.15);
    color: var(--warning);
}

/* ===== Spinner ===== */
.spinner {
    display: inline-block;
    width: 18px;
    height: 18px;
    border: 3px solid rgba(255, 255, 255, 0.3);
    border-top-color: #fff;
    border-radius: 50%;
    animation: spin 0.6s linear infinite;
}

@keyframes spin {
    to {
        transform: rotate(360deg);
    }
}

/* ===== Footer ===== */
.footer {
    text-align: center;
    margin-top: 1rem;
    color: var(--text-dim);
    font-size: 0.82rem;
    line-height: 1.6;
    opacity: 0.7;
}

/* ===== Responsive ===== */

/* Tablet-ish */
@media (max-width: 500px) {
    .title {
        font-size: 2rem;
    }

    .num-input {
        width: 56px;
        height: 56px;
        font-size: 1.3rem;
        border-radius: 12px;
    }

    .input-row {
        gap: 0.5rem;
    }

    .btn {
        padding: 0.7rem 1.2rem;
        font-size: 0.9rem;
    }

    .result-header .best-value {
        font-size: 2.4rem;
    }

    .card {
        padding: 1.2rem;
    }

    .result-expr {
        font-size: 0.95rem;
    }

    .result-val {
        font-size: 0.8rem;
        padding: 0.2rem 0.5rem;
    }
}

/* Small phones */
@media (max-width: 380px) {
    body {
        padding: 1rem 0.5rem;
    }

    .title {
        font-size: 1.7rem;
    }

    .subtitle {
        font-size: 0.88rem;
    }

    .num-input {
        width: 48px;
        height: 48px;
        font-size: 1.15rem;
        border-radius: 10px;
    }

    .num-input-wrapper label {
        font-size: 0.75rem;
    }

    .input-row {
        gap: 0.35rem;
    }

    .card {
        padding: 1rem 0.8rem;
        border-radius: 12px;
    }

    .btn {
        padding: 0.65rem 1rem;
        font-size: 0.85rem;
        border-radius: 10px;
    }

    .result-header .best-value {
        font-size: 2rem;
    }

    .result-expr {
        font-size: 0.85rem;
    }

    .result-item {
        padding: 0.6rem 0.7rem;
        gap: 0.5rem;
    }

    .result-val {
        font-size: 0.75rem;
        padding: 0.2rem 0.4rem;
    }

    .footer {
        font-size: 0.75rem;
    }
}