:root {
    --primary: #1a73e8;
    --primary-dark: #1557b0;
    --primary-light: #e8f0fe;
    --text: #202124;
    --text-light: #5f6368;
    --light-gray: #f8f9fa;
    --medium-gray: #dadce0;
    --dark-gray: #3c4043;
    --white: #ffffff;
    --success: #34a853;
    --warning: #f9ab00;
    --error: #d93025;
    --shadow: 0 1px 2px 0 rgba(60, 64, 67, 0.3), 0 1px 3px 1px rgba(60, 64, 67, 0.15);
    --radius: 8px;
    --transition: all 0.3s ease;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    line-height: 1.6;
    color: var(--text);
    background-color: #f5f7fa;
    padding: 20px;
}

.container {
    max-width: 1000px;
    margin: 0 auto;
    padding: 0 15px;
}

/* Header */
.header {
    text-align: center;
    margin-bottom: 2.5rem;
    padding: 2rem 0;
}

.logo {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 1rem;
}

.logo i {
    font-size: 2.5rem;
    color: var(--primary);
}

h1 {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text);
    margin: 0;
}

.subtitle {
    color: var(--text-light);
    font-size: 1.1rem;
    margin-top: 0.5rem;
}

/* Card */
.card {
    background: var(--white);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 2rem;
    margin-bottom: 2rem;
}

/* Form Elements */
.form-group {
    margin-bottom: 1.5rem;
}

label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: var(--text);
}

.input-group {
    display: flex;
    gap: 0.5rem;
}

.form-control {
    width: 100%;
    padding: 0.75rem 1rem;
    border: 1px solid var(--medium-gray);
    border-radius: var(--radius);
    font-size: 1rem;
    transition: var(--transition);
}

.form-control:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 2px rgba(26, 115, 232, 0.2);
}

.unit-select {
    min-width: 120px;
    background: var(--light-gray);
    border: 1px solid var(--medium-gray);
    border-radius: var(--radius);
    padding: 0 1rem;
    font-size: 0.9rem;
}

/* Range Input */
.range-container {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-top: 0.5rem;
}

input[type="range"] {
    -webkit-appearance: none;
    width: 100%;
    height: 6px;
    background: var(--medium-gray);
    border-radius: 3px;
    outline: none;
    margin: 0.5rem 0;
    flex: 1;
}

input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    width: 18px;
    height: 18px;
    background: var(--primary);
    border-radius: 50%;
    cursor: pointer;
    transition: var(--transition);
}

input[type="range"]:hover::-webkit-slider-thumb {
    transform: scale(1.1);
    box-shadow: 0 0 0 4px rgba(26, 115, 232, 0.2);
}

/* Buttons */
.calculate-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    color: var(--white);
    border: none;
    padding: 1rem 1.5rem;
    border-radius: var(--radius);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    width: 100%;
    transition: var(--transition);
    margin: 2rem 0 1rem;
}

.calculate-btn:hover {
    background: linear-gradient(135deg, var(--primary-dark), var(--primary));
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(26, 115, 232, 0.3);
}

.calculate-btn:active {
    transform: translateY(0);
}

/* Results */
.result-container {
    margin-top: 2rem;
    padding: 1.5rem;
    background: var(--primary-light);
    border-radius: var(--radius);
    border-left: 4px solid var(--primary);
}

.result-container h3 {
    margin-bottom: 1rem;
    color: var(--primary-dark);
}

.result-content {
    line-height: 1.6;
}

/* Info Card */
.info-card {
    background: var(--white);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 2rem;
    margin-bottom: 2rem;
}

.info-card h3 {
    margin-bottom: 1rem;
    color: var(--text);
    font-size: 1.1rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.info-list, .tips-list {
    list-style: none;
    margin-bottom: 1.5rem;
}

.info-list li, .tips-list li {
    margin-bottom: 0.5rem;
    padding-left: 1.5rem;
    position: relative;
}

.info-list li:before {
    content: "•";
    color: var(--primary);
    font-weight: bold;
    position: absolute;
    left: 0;
}

.tips-list li:before {
    content: "✓";
    color: var(--success);
    font-weight: bold;
    position: absolute;
    left: 0;
}

/* FAQ Section */
.faq-section {
    margin: 3rem 0;
}

.faq-section h2 {
    text-align: center;
    margin-bottom: 1.5rem;
    font-size: 1.5rem;
    color: var(--text);
}

.faq-item {
    margin-bottom: 0.75rem;
    border: 1px solid var(--medium-gray);
    border-radius: var(--radius);
    overflow: hidden;
}

.faq-question {
    width: 100%;
    text-align: left;
    padding: 1rem 1.5rem;
    background: var(--white);
    border: none;
    font-size: 1rem;
    font-weight: 500;
    color: var(--text);
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: var(--transition);
}

.faq-question:hover {
    background: var(--light-gray);
}

.faq-question i {
    transition: var(--transition);
}

.faq-question.active i {
    transform: rotate(180deg);
}

.faq-answer {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease;
    background: var(--light-gray);
}

.faq-answer p {
    padding: 1.5rem;
    margin: 0;
    border-top: 1px solid var(--medium-gray);
}

/* Footer */
.footer {
    text-align: center;
    padding: 2rem 0;
    color: var(--text-light);
    font-size: 0.9rem;
    border-top: 1px solid var(--medium-gray);
    margin-top: 2rem;
}

/* Utility Classes */
.hidden {
    display: none !important;
}

.hint {
    color: var(--text-light);
    font-size: 0.85rem;
    display: block;
    margin-top: 0.25rem;
}

/* Responsive Design */
@media (max-width: 768px) {
    .container {
        padding: 0 10px;
    }

    .header {
        padding: 1.5rem 0;
    }

    h1 {
        font-size: 1.75rem;
    }

    .subtitle {
        font-size: 1rem;
    }

    .card, .info-card {
        padding: 1.5rem;
    }

    .input-group {
        flex-direction: column;
    }

    .unit-select {
        width: 100%;
    }
}

/* Print Styles */
@media print {
    .calculate-btn, .faq-question {
        display: none !important;
    }

    .faq-answer {
        max-height: none !important;
        display: block !important;
        background: none;
        border: none;
    }

    .faq-answer p {
        padding: 0.5rem 0;
        border: none;
    }

    .result-container {
        border: 1px solid #000;
    }
}