/* ===== CSS Variables & Reset ===== */
:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --primary-light: #dbeafe;
    --accent: #059669;
    --accent-light: #d1fae5;
    --bg: #f8fafc;
    --card-bg: #ffffff;
    --text: #1e293b;
    --text-muted: #64748b;
    --border: #e2e8f0;
    --radius: 12px;
    --shadow: 0 1px 3px rgba(0,0,0,0.08), 0 1px 2px rgba(0,0,0,0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.08), 0 4px 6px -4px rgba(0,0,0,0.06);
}

*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
    min-height: 100vh;
}

/* ===== Header ===== */
header {
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    color: white;
    text-align: center;
    padding: 2rem 1rem;
    box-shadow: var(--shadow-lg);
}

header h1 {
    font-size: 1.8rem;
    font-weight: 700;
    margin-bottom: 0.3rem;
}

header .subtitle {
    font-size: 0.9rem;
    opacity: 0.85;
}

header .subtitle a {
    color: white;
    text-decoration: underline;
}

/* ===== Main Layout ===== */
main {
    max-width: 900px;
    margin: 0 auto;
    padding: 1.5rem 1rem;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

/* ===== Cards ===== */
.card {
    background: var(--card-bg);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 1.5rem;
    border: 1px solid var(--border);
}

.card h2 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 0.6rem;
    color: var(--text);
}

.step-num {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 28px;
    height: 28px;
    background: var(--primary);
    color: white;
    border-radius: 50%;
    font-size: 0.85rem;
    font-weight: 700;
    flex-shrink: 0;
}

/* ===== Rotor Type Selector ===== */
.rotor-type-selector {
    display: flex;
    gap: 1rem;
    margin-bottom: 1.2rem;
}

.rotor-type-btn {
    flex: 1;
    padding: 1rem;
    border: 2px solid var(--border);
    border-radius: var(--radius);
    background: var(--bg);
    cursor: pointer;
    text-align: center;
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--text-muted);
    transition: all 0.2s;
}

.rotor-type-btn:hover {
    border-color: var(--primary);
    color: var(--primary);
}

.rotor-type-btn.active {
    border-color: var(--primary);
    background: var(--primary-light);
    color: var(--primary);
}

.rotor-type-btn small {
    font-weight: 400;
    font-size: 0.8rem;
}

.rotor-icon {
    margin-bottom: 0.3rem;
    color: inherit;
}

/* ===== Parameter Rows ===== */
.param-group {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.param-row {
    display: flex;
    align-items: center;
    gap: 0.6rem;
    flex-wrap: wrap;
}

.param-row label {
    min-width: 140px;
    font-weight: 500;
    font-size: 0.9rem;
    color: var(--text);
}

.param-row input[type="number"],
.param-row input[type="text"],
.param-row select {
    padding: 0.5rem 0.75rem;
    border: 1.5px solid var(--border);
    border-radius: 8px;
    font-size: 0.9rem;
    width: 140px;
    transition: border-color 0.2s;
    background: white;
}

.param-row input:focus,
.param-row select:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.unit {
    font-size: 0.85rem;
    color: var(--text-muted);
    min-width: 40px;
}

.hidden {
    display: none !important;
}

/* ===== Buttons ===== */
.button-row {
    margin-top: 0.75rem;
}

.btn-calc {
    padding: 0.6rem 1.4rem;
    background: var(--primary);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.2s;
    margin-top: 0.5rem;
}

.btn-calc:hover {
    background: var(--primary-dark);
}

.btn-secondary {
    padding: 0.5rem 1.2rem;
    background: white;
    color: var(--text);
    border: 1.5px solid var(--border);
    border-radius: 8px;
    font-size: 0.85rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
}

.btn-secondary:hover {
    border-color: var(--primary);
    color: var(--primary);
}

/* ===== Preset Rotors ===== */
.preset-rotors {
    margin-top: 1rem;
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 0;
}

.preset-rotors summary {
    padding: 0.75rem 1rem;
    cursor: pointer;
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--primary);
    user-select: none;
}

.preset-rotors[open] summary {
    border-bottom: 1px solid var(--border);
}

.preset-rotors table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.8rem;
    overflow-x: auto;
    display: block;
}

.preset-rotors thead {
    display: table;
    width: 100%;
    table-layout: fixed;
}

.preset-rotors tbody {
    display: table;
    width: 100%;
    table-layout: fixed;
}

.preset-rotors th, .preset-rotors td {
    padding: 0.4rem 0.5rem;
    text-align: center;
    border-bottom: 1px solid var(--border);
}

.preset-rotors th {
    background: var(--bg);
    font-weight: 600;
    color: var(--text-muted);
    position: sticky;
    top: 0;
}

.preset-rotors tr {
    cursor: pointer;
    transition: background 0.15s;
}

.preset-rotors tbody tr:hover {
    background: var(--primary-light);
}

.btn-use-rotor {
    padding: 0.2rem 0.5rem;
    font-size: 0.75rem;
    background: var(--primary);
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
}

.btn-use-rotor:hover {
    background: var(--primary-dark);
}

/* ===== Calculation Section ===== */
.calc-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1.2rem;
}

.calc-block {
    background: var(--bg);
    border-radius: 8px;
    padding: 1rem;
    border: 1px solid var(--border);
}

.calc-block h3 {
    font-size: 0.95rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
    color: var(--text);
}

.result-display {
    margin-top: 0.5rem;
    font-size: 0.9rem;
    color: var(--accent);
    font-weight: 600;
    min-height: 1.4rem;
}

.instructions {
    font-size: 0.88rem;
    color: var(--text-muted);
    margin-bottom: 1rem;
    line-height: 1.5;
}

/* ===== Results Table ===== */
.results-section {
    margin-top: 1.5rem;
}

.results-section h3 {
    font-size: 1rem;
    margin-bottom: 0.75rem;
}

.results-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.9rem;
}

.results-table th, .results-table td {
    padding: 0.6rem 0.75rem;
    text-align: center;
    border: 1px solid var(--border);
}

.results-table th {
    background: var(--primary);
    color: white;
    font-weight: 600;
}

.results-table td:first-child,
.results-table th:first-child {
    text-align: left;
    font-weight: 600;
}

.results-table td {
    background: white;
}

.results-table td.highlight {
    background: var(--accent-light);
    color: var(--accent);
    font-weight: 700;
}

/* ===== Custom Sizes ===== */
.custom-sizes {
    margin-top: 1rem;
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    align-items: center;
}

.custom-sizes label {
    font-size: 0.85rem;
    font-weight: 500;
    width: 100%;
}

.custom-sizes input {
    padding: 0.5rem 0.75rem;
    border: 1.5px solid var(--border);
    border-radius: 8px;
    font-size: 0.9rem;
    flex: 1;
    min-width: 200px;
}

.custom-sizes input:focus {
    outline: none;
    border-color: var(--primary);
}

#custom-results {
    width: 100%;
    font-size: 0.88rem;
    color: var(--text);
    margin-top: 0.3rem;
}

#custom-results table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 0.5rem;
    font-size: 0.85rem;
}

#custom-results th, #custom-results td {
    padding: 0.4rem 0.6rem;
    text-align: center;
    border: 1px solid var(--border);
}

#custom-results th {
    background: var(--bg);
    font-weight: 600;
}

/* ===== Plot ===== */
#plot-container {
    margin-top: 1rem;
    min-height: 450px;
    width: 100%;
}

/* ===== K-Factor Section ===== */
.kfactor-display {
    text-align: center;
    padding: 0.5rem 0;
}

.kfactor-convert-row {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
    margin-bottom: 0.5rem;
}

#kfactor-results table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.85rem;
    margin-top: 0.5rem;
}

#kfactor-results th, #kfactor-results td {
    padding: 0.5rem 0.4rem;
    text-align: center;
    border: 1px solid var(--border);
}

#kfactor-results th {
    background: var(--bg);
    font-weight: 600;
    font-size: 0.8rem;
    color: var(--text-muted);
}

#kfactor-results td:first-child {
    text-align: left;
}

#kfactor-results tbody tr:hover {
    background: var(--primary-light);
}

/* ===== Protocol Designer ===== */
.protocol-step {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-bottom: 0.5rem;
    flex-wrap: wrap;
}

.protocol-step .step-label {
    font-weight: 600;
    font-size: 0.9rem;
    min-width: 55px;
}

.protocol-step input {
    padding: 0.5rem;
    border: 1.5px solid var(--border);
    border-radius: 8px;
    font-size: 0.85rem;
    width: 120px;
}

.protocol-step input:focus {
    outline: none;
    border-color: var(--primary);
}

.protocol-step select {
    padding: 0.5rem;
    border: 1.5px solid var(--border);
    border-radius: 8px;
    font-size: 0.85rem;
    background: white;
}

.btn-remove-step {
    width: 28px;
    height: 28px;
    display: flex;
    align-items: center;
    justify-content: center;
    border: 1.5px solid var(--border);
    border-radius: 50%;
    background: white;
    color: #ef4444;
    font-size: 1rem;
    cursor: pointer;
    transition: all 0.2s;
}

.btn-remove-step:hover {
    background: #fef2f2;
    border-color: #ef4444;
}

#protocol-results {
    margin-top: 1rem;
}

#protocol-results table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.85rem;
    margin-top: 0.5rem;
}

#protocol-results th, #protocol-results td {
    padding: 0.5rem;
    text-align: center;
    border: 1px solid var(--border);
}

#protocol-results th {
    background: var(--bg);
    font-weight: 600;
}

/* ===== Footer ===== */
footer {
    max-width: 900px;
    margin: 1rem auto 2rem;
    padding: 1.5rem;
    text-align: center;
    font-size: 0.8rem;
    color: var(--text-muted);
    line-height: 1.6;
}

footer a {
    color: var(--primary);
}

footer .disclaimer {
    margin-top: 0.5rem;
    font-style: italic;
    opacity: 0.7;
}

/* ===== Error Messages ===== */
.error-msg {
    color: #dc2626;
    font-size: 0.85rem;
    font-weight: 500;
    margin-top: 0.3rem;
}

.success-msg {
    color: var(--accent);
    font-size: 0.85rem;
    font-weight: 600;
    margin-top: 0.3rem;
}

/* ===== Responsive ===== */
@media (max-width: 600px) {
    header h1 {
        font-size: 1.3rem;
    }

    .rotor-type-selector {
        flex-direction: column;
    }

    .param-row {
        flex-direction: column;
        align-items: flex-start;
    }

    .param-row label {
        min-width: auto;
    }

    .param-row input, .param-row select {
        width: 100%;
    }

    .protocol-step {
        flex-direction: column;
        align-items: flex-start;
        padding: 0.5rem;
        background: var(--bg);
        border-radius: 8px;
    }

    .protocol-step input, .protocol-step select {
        width: 100%;
    }

    .preset-rotors table {
        font-size: 0.7rem;
    }
}