:root {
    --bg: #f5f7fb;
    --panel: #ffffff;
    --text: #18202f;
    --muted: #627089;
    --primary: #176b87;
    --primary-dark: #104e63;
    --accent: #f59f00;
    --border: #dce3ee;
    --success: #0f7b4f;
    --warning: #9a5b00;
    --danger: #a33333;
}

* {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    font-family: Arial, Helvetica, sans-serif;
    color: var(--text);
    background: var(--bg);
    line-height: 1.6;
}

.site-header {
    background: linear-gradient(135deg, #176b87, #46a39a);
    color: #ffffff;
    padding: 24px 20px 56px;
}

.top-nav {
    display: flex;
    justify-content: center;
    gap: 14px;
    flex-wrap: wrap;
    margin-bottom: 42px;
}

.top-nav a {
    color: #ffffff;
    text-decoration: none;
    font-weight: 700;
    border: 1px solid rgba(255, 255, 255, 0.45);
    padding: 8px 14px;
    border-radius: 6px;
}

.top-nav a:hover {
    background: rgba(255, 255, 255, 0.15);
}

.hero {
    max-width: 820px;
    margin: 0 auto;
    text-align: center;
}

.eyebrow {
    margin: 0 0 8px;
    color: #fff3cd;
    font-weight: 700;
    text-transform: uppercase;
    font-size: 0.82rem;
}

.hero h1 {
    margin: 0 0 16px;
    font-size: clamp(2rem, 4vw, 3.4rem);
}

.hero p:last-child {
    max-width: 680px;
    margin: 0 auto;
    color: #eefcff;
}

.page-grid {
    width: min(1120px, calc(100% - 32px));
    margin: -30px auto 32px;
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 22px;
}

.calculator-panel {
    background: var(--panel);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 24px;
    box-shadow: 0 14px 30px rgba(30, 45, 70, 0.12);
}

.panel-heading {
    margin-bottom: 20px;
}

.method-label {
    color: var(--primary);
    font-size: 0.82rem;
    font-weight: 700;
    text-transform: uppercase;
}

.panel-heading h2 {
    margin: 4px 0 8px;
    font-size: 1.35rem;
}

.panel-heading p {
    margin: 0;
    color: var(--muted);
}

.bmi-form {
    display: grid;
    gap: 10px;
}

label {
    font-weight: 700;
}

input {
    width: 100%;
    min-height: 44px;
    border: 1px solid var(--border);
    border-radius: 6px;
    padding: 10px 12px;
    font: inherit;
}

input:focus {
    outline: 3px solid rgba(23, 107, 135, 0.18);
    border-color: var(--primary);
}

button {
    margin-top: 10px;
    min-height: 46px;
    border: 0;
    border-radius: 6px;
    background: var(--primary);
    color: #ffffff;
    font: inherit;
    font-weight: 700;
    cursor: pointer;
}

button:hover {
    background: var(--primary-dark);
}

.result-box {
    margin-top: 18px;
}

.result-card {
    border-left: 5px solid var(--primary);
    background: #f8fbfd;
    border-radius: 6px;
    padding: 16px;
}

.result-card h3 {
    margin: 0 0 10px;
}

.result-card p {
    margin: 6px 0;
}

.status-underweight,
.status-overweight {
    color: var(--warning);
    font-weight: 700;
}

.status-normal {
    color: var(--success);
    font-weight: 700;
}

.status-obese {
    color: var(--danger);
    font-weight: 700;
}

.error {
    color: var(--danger);
    font-weight: 700;
}

.site-footer {
    text-align: center;
    color: var(--muted);
    padding: 18px;
}

@media (max-width: 780px) {
    .page-grid {
        grid-template-columns: 1fr;
        margin-top: -22px;
    }

    .calculator-panel {
        padding: 20px;
    }
}