:root {
    --primary: #0ea5e9; /* ZM Blue */
    --primary-dark: #0284c7;
    --text: #334155;
    --bg: #f8fafc;
    --white: #ffffff;
    --border: #e2e8f0;
}

* { box-sizing: border-box; }

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg);
    color: var(--text);
    margin: 0;
    padding: 0;
    line-height: 1.6;
}

/* UNIVERSAL NAV */
.navbar {
    background: var(--white);
    border-bottom: 1px solid var(--border);
    padding: 15px 0;
}
.nav-container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}
.brand {
    font-weight: 800;
    font-size: 20px;
    text-decoration: none;
    color: var(--primary);
}
.nav-links a {
    text-decoration: none;
    color: var(--text);
    margin-left: 20px;
    font-size: 14px;
    font-weight: 500;
}
.nav-links a:hover { color: var(--primary); }
.nav-btn {
    background: var(--primary);
    color: white !important;
    padding: 8px 16px;
    border-radius: 6px;
}

/* MAIN CONTENT LAYOUT */
.main-wrapper {
    max-width: 800px;
    margin: 40px auto;
    padding: 0 20px;
    min-height: 60vh; /* Keeps footer at bottom */
}

/* TOOL STYLES */
.tool-card {
    background: var(--white);
    padding: 30px;
    border-radius: 12px;
    border: 1px solid var(--border);
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.05);
}
.input-group { margin-bottom: 20px; }
label { display: block; font-weight: 600; margin-bottom: 8px; font-size: 14px; }
.form-control {
    width: 100%;
    padding: 12px;
    border: 1px solid var(--border);
    border-radius: 8px;
    font-size: 16px;
}
.results-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
    gap: 15px;
    margin-top: 25px;
    background: #f1f5f9;
    padding: 20px;
    border-radius: 8px;
}
.res-box { text-align: center; }
.res-label { font-size: 11px; text-transform: uppercase; color: #64748b; letter-spacing: 0.5px; }
.res-val { font-size: 18px; font-weight: bold; color: #0f172a; }

/* FOOTER */
footer {
    background: var(--white);
    border-top: 1px solid var(--border);
    padding: 30px 0;
    text-align: center;
    font-size: 13px;
    color: #64748b;
    margin-top: 60px;
}