/* ===== 기본 리셋 & 변수 ===== */
    *, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

    :root {
    --bg-from: #a8d8f5;
    --bg-to: #dff2ff;
    --glass: rgba(255, 255, 255, 0.75);
    --glass-border: rgba(255, 255, 255, 0.90);
    --shadow: 0 8px 32px rgba(52, 140, 210, 0.18);
    --shadow-hover: 0 12px 40px rgba(52, 140, 210, 0.30);
    --blue: #2e8fd4;
    --blue-dark: #1a6fac;
    --blue-light: #b8e0f7;
    --blue-xlight: #e3f5ff;
    --text: #0f2d42;
    --text-mid: #2a5470;
    --text-light: #5e9abf;
    --radius: 18px;
    --radius-sm: 10px;
    --transition: 0.2s ease;
    }

    html { font-size: 16px; }

    body {
    font-family: 'Noto Sans KR', sans-serif;
    background: linear-gradient(145deg, var(--bg-from) 0%, var(--bg-to) 100%);
    min-height: 100vh;
    color: var(--text);
    }

    /* 배경 장식 */
    body::before {
    content: '';
    position: fixed;
    top: -200px; right: -200px;
    width: 600px; height: 600px;
    border-radius: 50%;
    background: radial-gradient(circle, rgba(255,255,255,0.5) 0%, transparent 70%);
    pointer-events: none;
    z-index: 0;
    }
    body::after {
    content: '';
    position: fixed;
    bottom: -150px; left: -150px;
    width: 500px; height: 500px;
    border-radius: 50%;
    background: radial-gradient(circle, rgba(74,158,218,0.1) 0%, transparent 70%);
    pointer-events: none;
    z-index: 0;
    }

    .page-wrapper {
    position: relative;
    z-index: 1;
    max-width: 900px;
    margin: 0 auto;
    padding: 0 16px 60px;
    }

    /* ===== 헤더 ===== */
    .site-header {
    padding: 36px 0 24px;
    text-align: center;
    }
    .header-inner {
    display: inline-flex;
    align-items: center;
    gap: 16px;
    }
    .header-icon {
    width: 60px; height: 60px;
    background: linear-gradient(135deg, var(--blue) 0%, #7dc4f0 100%);
    border-radius: 18px;
    display: flex; align-items: center; justify-content: center;
    font-size: 26px;
    font-family: 'Nunito', sans-serif;
    font-weight: 800;
    color: #fff;
    box-shadow: 0 6px 20px rgba(74, 158, 218, 0.35);
    flex-shrink: 0;
    }
    .site-title {
    font-size: 1.7rem;
    font-weight: 700;
    color: var(--text);
    line-height: 1.2;
    }
    .site-subtitle {
    font-size: 0.85rem;
    color: var(--text-light);
    font-family: 'Nunito', sans-serif;
    font-weight: 600;
    letter-spacing: 0.05em;
    margin-top: 2px;
    }

    /* ===== 카드 기본 ===== */
    .card {
    background: var(--glass);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1.5px solid var(--glass-border);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    }

    /* ===== 카테고리 탭 ===== */
    .category-nav {
    display: flex;
    gap: 8px;
    overflow-x: auto;
    padding: 4px 2px 12px;
    scrollbar-width: none;
    -ms-overflow-style: none;
    }
    .category-nav::-webkit-scrollbar { display: none; }

    .cat-btn {
    flex-shrink: 0;
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 9px 16px;
    border-radius: 40px;
    border: 1.5px solid rgba(74, 158, 218, 0.25);
    background: var(--glass);
    backdrop-filter: blur(8px);
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-mid);
    cursor: pointer;
    transition: var(--transition);
    white-space: nowrap;
    font-family: 'Noto Sans KR', sans-serif;
    }
    .cat-btn:hover {
    background: var(--blue-light);
    border-color: var(--blue);
    color: var(--blue-dark);
    transform: translateY(-1px);
    }
    .cat-btn.active {
    background: linear-gradient(135deg, var(--blue) 0%, #7dc4f0 100%);
    border-color: transparent;
    color: #fff;
    box-shadow: 0 4px 14px rgba(74, 158, 218, 0.4);
    font-weight: 700;
    }
    .cat-icon { font-size: 1rem; }

    /* ===== 입력 패널 ===== */
    .input-panel {
    padding: 20px 22px;
    margin-bottom: 14px;
    }
    .input-row {
    display: flex;
    align-items: flex-end;
    gap: 12px;
    flex-wrap: wrap;
    }
    .input-group {
    flex: 2;
    min-width: 160px;
    }
    .unit-select-group {
    flex: 1.4;
    min-width: 140px;
    }
    .input-label {
    display: block;
    font-size: 0.78rem;
    font-weight: 600;
    color: var(--text-light);
    margin-bottom: 6px;
    letter-spacing: 0.03em;
    text-transform: uppercase;
    }
    .value-input {
    width: 100%;
    padding: 12px 16px;
    font-size: 1.25rem;
    font-weight: 600;
    font-family: 'Nunito', sans-serif;
    color: var(--text);
    background: rgba(255, 255, 255, 0.8);
    border: 2px solid rgba(74, 158, 218, 0.25);
    border-radius: var(--radius-sm);
    outline: none;
    transition: var(--transition);
    }
    .value-input:focus {
    border-color: var(--blue);
    background: #fff;
    box-shadow: 0 0 0 4px rgba(74, 158, 218, 0.12);
    }
    .value-input::placeholder { color: #b0cfe0; font-weight: 400; }
    .value-input::-webkit-outer-spin-button,
    .value-input::-webkit-inner-spin-button { -webkit-appearance: none; }
    .value-input[type=number] { -moz-appearance: textfield; }

    .unit-select {
    width: 100%;
    padding: 12px 36px 12px 14px;
    font-size: 0.95rem;
    font-weight: 600;
    font-family: 'Noto Sans KR', sans-serif;
    color: var(--text);
    background: rgba(255, 255, 255, 0.8) url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8' viewBox='0 0 12 8'%3E%3Cpath d='M1 1l5 5 5-5' stroke='%234a9eda' stroke-width='2' fill='none' stroke-linecap='round'/%3E%3C/svg%3E") no-repeat right 14px center;
    border: 2px solid rgba(74, 158, 218, 0.25);
    border-radius: var(--radius-sm);
    outline: none;
    cursor: pointer;
    appearance: none;
    -webkit-appearance: none;
    transition: var(--transition);
    }
    .unit-select:focus {
    border-color: var(--blue);
    background-color: #fff;
    box-shadow: 0 0 0 4px rgba(74, 158, 218, 0.12);
    }

    .swap-btn {
    flex-shrink: 0;
    width: 46px; height: 46px;
    border-radius: 50%;
    border: 2px solid rgba(74, 158, 218, 0.3);
    background: var(--blue-xlight);
    color: var(--blue);
    font-size: 1.2rem;
    font-weight: 700;
    cursor: pointer;
    transition: var(--transition);
    display: flex; align-items: center; justify-content: center;
    margin-bottom: 1px;
    }
    .swap-btn:hover {
    background: var(--blue);
    color: #fff;
    border-color: var(--blue);
    transform: rotate(180deg);
    box-shadow: 0 4px 12px rgba(74, 158, 218, 0.4);
    }

    /* ===== 결과 헤더 ===== */
    .results-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 4px 10px;
    flex-wrap: wrap;
    gap: 6px;
    }
    .results-title {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-mid);
    }
    .results-hint {
    font-size: 0.75rem;
    color: var(--text-light);
    }

    /* ===== 결과 그리드 ===== */
    .results-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(190px, 1fr));
    gap: 10px;
    }

    .result-card {
    background: var(--glass);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1.5px solid var(--glass-border);
    border-radius: var(--radius-sm);
    box-shadow: 0 4px 16px rgba(74, 158, 218, 0.1);
    padding: 10px 12px;
    cursor: pointer;
    transition: var(--transition);
    position: relative;
    overflow: hidden;
    }
    .result-card::before {
    content: '';
    position: absolute;
    top: 0; left: 0; right: 0;
    height: 3px;
    background: linear-gradient(90deg, var(--blue) 0%, #7dc4f0 100%);
    opacity: 0;
    transition: var(--transition);
    }
    .result-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-hover);
    border-color: rgba(74, 158, 218, 0.4);
    }
    .result-card:hover::before { opacity: 1; }
    .result-card.active-unit {
    background: linear-gradient(135deg, rgba(74,158,218,0.12) 0%, rgba(125,196,240,0.08) 100%);
    border-color: var(--blue);
    }
    .result-card.active-unit::before { opacity: 1; }

    .result-unit-name {
    font-size: 0.72rem;
    color: var(--text-light);
    font-weight: 600;
    margin-bottom: 5px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    }
    .result-bottom {
    display: flex;
    align-items: baseline;
    gap: 5px;
    flex-wrap: wrap;
    }
    .result-symbol {
    font-family: 'Nunito', sans-serif;
    font-weight: 800;
    font-size: 1.05rem;
    color: #fff;
    background: linear-gradient(135deg, var(--blue) 0%, #5ab8f0 100%);
    padding: 2px 10px;
    border-radius: 20px;
    letter-spacing: 0.02em;
    box-shadow: 0 2px 8px rgba(46, 143, 212, 0.35);
    white-space: nowrap;
    flex-shrink: 0;
    }
    .result-value {
    font-size: 1.25rem;
    font-weight: 700;
    font-family: 'Nunito', sans-serif;
    color: var(--text);
    word-break: break-all;
    line-height: 1.3;
    }
    .result-value.zero { color: var(--text-light); }

    .copy-hint {
    font-size: 0.65rem;
    color: var(--text-light);
    margin-top: 3px;
    opacity: 0;
    transition: var(--transition);
    }
    .result-card:hover .copy-hint { opacity: 1; }

    /* ===== 빈 상태 ===== */
    .empty-state {
    text-align: center;
    padding: 60px 20px;
    color: var(--text-light);
    }
    .empty-icon { font-size: 3rem; margin-bottom: 14px; }
    .empty-state p { font-size: 1rem; line-height: 1.8; }

    /* ===== 토스트 ===== */
    .toast {
    position: fixed;
    bottom: 30px; left: 50%;
    transform: translateX(-50%) translateY(20px);
    background: rgba(30, 58, 79, 0.92);
    color: #fff;
    padding: 10px 22px;
    border-radius: 30px;
    font-size: 0.875rem;
    font-weight: 500;
    pointer-events: none;
    opacity: 0;
    transition: all 0.3s ease;
    z-index: 9999;
    white-space: nowrap;
    }
    .toast.show {
    opacity: 1;
    transform: translateX(-50%) translateY(0);
    }

    /* ===== 푸터 ===== */
    .site-footer {
    margin-top: 40px;
    padding: 0 4px;
    }
    .site-footer p {
    font-size: 0.72rem;
    color: var(--text-light);
    line-height: 1.7;
    }

    /* ===== 반응형 ===== */
    @media (max-width: 600px) {
    .site-title { font-size: 1.3rem; }
    .header-icon { width: 48px; height: 48px; font-size: 20px; }
    .results-grid { grid-template-columns: repeat(2, 1fr); }
    .input-row { flex-direction: column; }
    .input-group, .unit-select-group { width: 100%; flex: none; }
    .swap-btn { align-self: flex-end; margin-top: -8px; }
    }