:root {
    --primary-color: #2563EB; /* Deep Blue */
    --primary-hover: #1D4ED8;
    --primary-light: #EFF6FF;
    
    --secondary-color: #64748B;
    --secondary-hover: #475569;
    --secondary-light: #F1F5F9;
    
    --danger-color: #EF4444; /* Obese */
    --danger-light: #FEE2E2;
    
    --warning-color: #F59E0B; /* Overweight */
    --warning-light: #FEF3C7;
    
    --success-color: #10B981; /* Normal */
    --success-light: #D1FAE5;
    
    --info-color: #3B82F6; /* Underweight */
    --info-light: #DBEAFE;
    
    --background-color: #F8FAFC; /* Soft light background */
    --card-bg: #FFFFFF;
    --text-main: #1E293B;
    --text-muted: #64748B;
    --border-color: #E2E8F0;
    
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 18px;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Inter', sans-serif;
}

body {
    background-color: var(--background-color);
    color: var(--text-main);
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

/* Header */
.header {
    background-color: var(--card-bg);
    padding: 1.25rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 100;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

.nav ul {
    list-style: none;
    display: flex;
    gap: 2.5rem;
}

.nav a {
    text-decoration: none;
    color: var(--text-muted);
    font-weight: 500;
    transition: color 0.2s ease;
}

.nav a:hover, .nav a.active {
    color: var(--primary-color);
}

.header-contact {
    display: flex;
    gap: 1.5rem;
}

.contact-link {
    text-decoration: none;
    color: var(--text-muted);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.9rem;
    font-weight: 500;
    transition: color 0.2s ease;
}

.contact-link:hover {
    color: var(--primary-color);
}

/* Main Content */
.main-content {
    flex: 1;
    display: flex;
    justify-content: center;
    align-items: flex-start;
    padding: 3rem 1rem;
}

.calculator-container {
    max-width: 700px;
    width: 100%;
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

.card {
    background-color: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    padding: 2.5rem;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.card:hover {
    box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
}

.card-header {
    margin-bottom: 2rem;
}

.card-header h2 {
    font-size: 1.75rem;
    color: var(--text-main);
    font-weight: 700;
    margin-bottom: 0.25rem;
}

.subtitle {
    color: var(--text-muted);
    font-size: 0.95rem;
}

.flex-between {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

/* Inputs */
.input-header {
    margin-bottom: 0.75rem;
}

.input-header label {
    font-weight: 600;
    color: var(--text-main);
    font-size: 1.05rem;
}

.radio-toggle {
    display: flex;
    background-color: var(--secondary-light);
    border-radius: var(--radius-sm);
    padding: 0.25rem;
}

.radio-toggle input[type="radio"] {
    display: none;
}

.radio-toggle label {
    padding: 0.35rem 1rem;
    cursor: pointer;
    border-radius: var(--radius-sm);
    font-weight: 600;
    font-size: 0.85rem;
    color: var(--text-muted);
    transition: all 0.2s ease;
}

.radio-toggle input[type="radio"]:checked + label {
    background-color: white;
    color: var(--primary-color);
    box-shadow: var(--shadow-sm);
}

.input-wrapper {
    display: flex;
    align-items: center;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 0.25rem 1rem;
    background-color: var(--background-color);
    transition: all 0.3s ease;
}

.input-wrapper:focus-within {
    border-color: var(--primary-color);
    background-color: white;
    box-shadow: 0 0 0 4px rgba(37, 99, 235, 0.1);
}

.form-input {
    flex: 1;
    border: none;
    background: transparent;
    padding: 1rem 0;
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-main);
    outline: none;
}

.form-input::placeholder {
    color: #94A3B8;
    font-weight: 400;
}

.unit-label {
    font-weight: 600;
    color: var(--text-muted);
    margin-left: 0.5rem;
}

.validation-message {
    color: var(--danger-color);
    font-size: 0.85rem;
    margin-top: 0.75rem;
    font-weight: 500;
    min-height: 20px;
}

/* Buttons */
.action-buttons {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
    margin-top: 1rem;
}

.btn {
    padding: 0.875rem 1.5rem;
    border: none;
    border-radius: var(--radius-sm);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

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

.btn-primary {
    background-color: var(--primary-color);
    color: white;
}
.btn-primary:hover {
    background-color: var(--primary-hover);
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
}

.btn-secondary {
    background-color: var(--secondary-light);
    color: var(--text-main);
}
.btn-secondary:hover {
    background-color: #E2E8F0;
}

.btn-danger-outline {
    background-color: transparent;
    color: var(--text-muted);
    border: 1px solid var(--border-color);
}
.btn-danger-outline:hover {
    background-color: #FEF2F2;
    border-color: var(--danger-color);
    color: var(--danger-color);
}

.btn-icon {
    background-color: var(--secondary-light);
    color: var(--text-muted);
    padding: 0.5rem 1rem;
    font-size: 0.9rem;
}
.btn-icon:hover {
    background-color: var(--primary-light);
    color: var(--primary-color);
}

/* Results Section */
.result-card.hidden {
    display: none;
}

.result-card {
    animation: fadeInSlideUp 0.5s cubic-bezier(0.175, 0.885, 0.32, 1.275) forwards;
}

.result-display {
    display: flex;
    flex-direction: column;
    align-items: center;
    margin-bottom: 2rem;
    padding: 1.5rem;
    background-color: var(--background-color);
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    transition: background-color 0.4s ease;
}

.bmi-value-circle {
    font-size: 3.5rem;
    font-weight: 800;
    line-height: 1;
    margin-bottom: 0.5rem;
    color: var(--text-main);
}

.bmi-category {
    font-size: 1.25rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

/* BMI Meter */
.bmi-meter {
    margin: 2.5rem 0 1.5rem 0;
    position: relative;
}

.meter-bar {
    display: flex;
    height: 14px;
    border-radius: 7px;
    background: #E2E8F0;
    position: relative;
    overflow: visible;
}

.meter-segment { flex: 1; }
.segment-underweight { background-color: var(--info-color); border-top-left-radius: 7px; border-bottom-left-radius: 7px; }
.segment-normal { background-color: var(--success-color); }
.segment-overweight { background-color: var(--warning-color); }
.segment-obese { background-color: var(--danger-color); border-top-right-radius: 7px; border-bottom-right-radius: 7px; }

.meter-marker {
    position: absolute;
    top: -26px;
    transform: translateX(-50%);
    font-size: 1.75rem;
    color: var(--text-main);
    transition: left 0.8s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    z-index: 10;
}

.meter-labels {
    display: flex;
    justify-content: space-between;
    margin-top: 0.75rem;
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--text-muted);
}
.meter-labels span {
    flex: 1;
    text-align: center;
}

/* Healthy Range Box */
.healthy-range-box {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
    padding: 1.25rem;
    background-color: var(--primary-light);
    border-radius: var(--radius-sm);
    color: var(--primary-color);
    font-size: 1rem;
    font-weight: 500;
    margin-top: 2rem;
}

.font-bold {
    font-weight: 700;
}

/* Toast */
.toast {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    background-color: var(--text-main);
    color: white;
    padding: 1rem 1.5rem;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    gap: 0.75rem;
    box-shadow: var(--shadow-lg);
    z-index: 1000;
    transition: all 0.4s cubic-bezier(0.68, -0.55, 0.265, 1.55);
    transform: translateY(150%);
    opacity: 0;
}
.toast.show {
    transform: translateY(0);
    opacity: 1;
}
.toast.success i { color: var(--success-color); }
.toast.danger i { color: var(--danger-color); }

/* Footer */
.footer {
    background-color: var(--card-bg);
    padding: 2rem;
    text-align: center;
    border-top: 1px solid var(--border-color);
    margin-top: auto;
}
.text-danger { color: var(--danger-color); }
.footer-contact {
    display: flex;
    justify-content: center;
    gap: 2rem;
    font-size: 0.95rem;
    margin-top: 1rem;
}
.footer-contact a {
    color: var(--text-muted);
    text-decoration: none;
    transition: color 0.2s ease;
}
.footer-contact a:hover {
    color: var(--primary-color);
}

/* Animations */
@keyframes fadeInSlideUp {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}