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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: #f5f5f5;
    color: #333;
    line-height: 1.6;
}

.container {
    max-width: 1000px;
    margin: 0 auto;
    padding: 20px;
}

header {
    text-align: center;
    margin-bottom: 30px;
}

h1 {
    font-size: 2.5rem;
    font-weight: 600;
    color: #2c3e50;
    margin-bottom: 5px;
}

.subtitle {
    font-size: 1rem;
    color: #7f8c8d;
}

.mode-selector {
    display: flex;
    gap: 10px;
    margin-bottom: 30px;
    justify-content: center;
}

.mode-btn {
    padding: 12px 24px;
    border: 2px solid #e0e0e0;
    background: white;
    color: #555;
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    border-radius: 8px;
}

.mode-btn:hover {
    border-color: #3498db;
    color: #3498db;
}

.mode-btn.active {
    background: #3498db;
    border-color: #3498db;
    color: white;
}

.calculator-content {
    background: white;
    border-radius: 12px;
    padding: 30px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.05);
}

.mode-panel {
    display: none;
}

.mode-panel.active {
    display: block;
}

.input-section {
    margin-bottom: 40px;
}

.helper-text {
    color: #7f8c8d;
    margin-bottom: 16px;
    font-size: 0.95rem;
}

h2 {
    font-size: 1.3rem;
    font-weight: 600;
    color: #2c3e50;
    margin-bottom: 20px;
}

.input-group {
    display: grid;
    grid-template-columns: 100px 1fr 60px;
    align-items: center;
    gap: 15px;
    margin-bottom: 15px;
}

.input-group label {
    font-weight: 500;
    color: #555;
}

.input-group input {
    padding: 12px 16px;
    border: 2px solid #e0e0e0;
    border-radius: 6px;
    font-size: 1rem;
    outline: none;
}

.input-group input:focus {
    border-color: #3498db;
}

.input-group .unit {
    color: #7f8c8d;
    font-size: 0.9rem;
}

.output-section {
    border-top: 2px solid #f0f0f0;
    padding-top: 30px;
}

.output-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
}

.output-item {
    background: #f8f9fa;
    padding: 20px;
    border-radius: 8px;
    text-align: center;
}

.output-label {
    font-size: 0.85rem;
    color: #7f8c8d;
    margin-bottom: 8px;
    font-weight: 500;
}

.output-value {
    font-size: 2rem;
    font-weight: 600;
    color: #2c3e50;
    margin-bottom: 5px;
    word-break: break-all;
}

.output-unit {
    font-size: 0.9rem;
    color: #95a5a6;
}

.conversion-row {
    display: flex;
    gap: 12px;
    flex-wrap: wrap;
    margin-top: 10px;
}

.conversion-note {
    background: #f4f7fb;
    padding: 10px 12px;
    border-radius: 6px;
    color: #2c3e50;
    font-size: 0.95rem;
}

.conversion-label {
    font-weight: 600;
    margin-right: 6px;
}

.input-group.multi {
    grid-template-columns: 100px 1fr 1fr;
}

.split-input {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 0 10px;
    border: 2px solid #e0e0e0;
    border-radius: 6px;
    background: #fff;
}

.split-input:focus-within {
    border-color: #3498db;
}

.split-input input {
    border: none;
    padding: 12px 6px;
    font-size: 1rem;
    outline: none;
    width: 100%;
}

.dual-pane {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 20px;
    margin-bottom: 20px;
}

.panel-block {
    background: #f8f9fa;
    padding: 16px;
    border-radius: 8px;
    height: 100%;
}

.placeholder {
    text-align: center;
    padding: 60px 20px;
    color: #95a5a6;
    font-size: 1.1rem;
}

/* Remove spinner from number inputs */
input[type="number"]::-webkit-inner-spin-button,
input[type="number"]::-webkit-outer-spin-button {
    -webkit-appearance: none;
    margin: 0;
}

input[type="number"] {
    -moz-appearance: textfield;
}

@media (max-width: 768px) {
    h1 {
        font-size: 2rem;
    }

    .mode-selector {
        flex-wrap: wrap;
    }

    .mode-btn {
        flex: 1 1 auto;
        min-width: 120px;
    }

    .calculator-content {
        padding: 20px;
    }

    .input-group {
        grid-template-columns: 80px 1fr 50px;
        gap: 10px;
    }

    .input-group.multi {
        grid-template-columns: 80px 1fr 1fr;
    }

    .dual-pane {
        grid-template-columns: 1fr;
    }

    .output-grid {
        grid-template-columns: 1fr;
    }

    .output-value {
        font-size: 1.5rem;
    }
}