/* --- MASTER STYLESHEET --- */
:root {
    --primary: #2563eb;       /* Professional Blue */
    --primary-dark: #1e40af;
    --bg-color: #f3f4f6;
    --card-bg: #ffffff;
    --text-main: #1f2937;
    --text-muted: #6b7280;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
}

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

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

/* NAVBAR */
header { background: var(--card-bg); border-bottom: 1px solid #e5e7eb; padding: 1rem 0; position: sticky; top: 0; z-index: 50; }
.nav-container { max-width: 1200px; margin: 0 auto; padding: 0 1.5rem; display: flex; justify-content: space-between; align-items: center; }
.logo { font-size: 1.5rem; font-weight: 800; color: var(--primary); text-decoration: none; letter-spacing: -0.5px; }
.nav-link { color: var(--text-main); text-decoration: none; font-weight: 500; margin-left: 20px; transition: 0.2s; }
.nav-link:hover { color: var(--primary); }

/* MAIN LAYOUT */
main { flex: 1; max-width: 1200px; margin: 0 auto; padding: 2rem 1.5rem; width: 100%; }

/* GRID (FOR HOME PAGE) */
.hero-section { text-align: center; margin-bottom: 3rem; }
.hero-title { font-size: 2.5rem; margin-bottom: 0.5rem; color: #111827; }
.hero-sub { color: var(--text-muted); font-size: 1.1rem; }

.tools-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 1.5rem; }
.tool-card { background: var(--card-bg); padding: 2rem; border-radius: 12px; box-shadow: var(--shadow); text-decoration: none; color: inherit; transition: transform 0.2s, box-shadow 0.2s; border: 1px solid transparent; }
.tool-card:hover { transform: translateY(-4px); box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1); border-color: var(--primary); }
.icon { font-size: 2rem; margin-bottom: 1rem; display: block; }
.card-title { font-size: 1.25rem; font-weight: 700; margin-bottom: 0.5rem; }
.card-desc { color: var(--text-muted); font-size: 0.9rem; line-height: 1.5; }

/* CALCULATOR INTERFACE (FOR INNER PAGES) */
.calc-container { background: var(--card-bg); max-width: 500px; margin: 2rem auto; padding: 2.5rem; border-radius: 16px; box-shadow: var(--shadow); }
.input-group { margin-bottom: 1.5rem; }
label { display: block; font-weight: 600; margin-bottom: 0.5rem; color: #374151; }
input { width: 100%; padding: 0.75rem; border: 1px solid #d1d5db; border-radius: 8px; font-size: 1rem; transition: border 0.2s; }
input:focus { outline: none; border-color: var(--primary); ring: 2px solid var(--primary); }
.btn-calc { width: 100%; background: var(--primary); color: white; padding: 1rem; border: none; border-radius: 8px; font-size: 1rem; font-weight: 600; cursor: pointer; transition: background 0.2s; }
.btn-calc:hover { background: var(--primary-dark); }
.result-box { margin-top: 1.5rem; padding: 1.5rem; background: #eff6ff; border-radius: 8px; border-left: 4px solid var(--primary); display: none; }
.result-text { font-size: 1.1rem; font-weight: 500; color: #1e3a8a; }
.result-big { display: block; font-size: 2rem; font-weight: 800; margin-top: 0.5rem; }

/* FOOTER */
footer { background: #111827; color: #9ca3af; text-align: center; padding: 2rem 0; margin-top: auto; }