:root {
    --primary: #2563eb; --bg: #f8fafc; --card-bg: #ffffff;
    --text: #334155; --border: #e2e8f0; --sidebar-bg: #ffffff;
    --brand: #1e293b; --input-bg: #ffffff;
}
[data-theme="dark"] {
    --primary: #60a5fa; --bg: #0f172a; --card-bg: #1e293b;
    --text: #f1f5f9; --border: #334155; --sidebar-bg: #1e293b;
    --brand: #f8fafc; --input-bg: #334155;
}
body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background-color: var(--bg); color: var(--text); margin: 0;
    display: flex; flex-direction: column; min-height: 100vh; transition: 0.3s;
}
.header-bar { display: flex; justify-content: space-between; align-items: center; padding: 10px 20px; background: var(--card-bg); border-bottom: 1px solid var(--border); }
.theme-btn { background: transparent; border: 1px solid var(--border); color: var(--text); padding: 6px 12px; cursor: pointer; border-radius: 4px; font-size: 0.8em; }

/* 2-COLUMN LAYOUT (Sidebar + Main) */
.container { 
    display: grid; 
    grid-template-columns: 260px 1fr; 
    gap: 30px; 
    max-width: 1000px; 
    margin: 30px auto; 
    padding: 0 20px; 
    width: 100%; 
    box-sizing: border-box; 
}
@media (max-width: 768px) { .container { grid-template-columns: 1fr; } .nav-sidebar { display: none; } }

.nav-sidebar { background: var(--sidebar-bg); padding: 20px; border-radius: 8px; border: 1px solid var(--border); position: sticky; top: 20px; height: fit-content; }
.brand h2 { margin: 0; color: var(--brand); font-size: 1.4em; }
.nav-cat { font-size: 0.7em; text-transform: uppercase; color: #94a3b8; font-weight: 800; margin: 15px 0 5px 0; }
.nav-link { display: block; padding: 8px 10px; color: var(--text); text-decoration: none; border-radius: 5px; font-size: 0.9em; }
.nav-link:hover, .nav-link.active { background: var(--border); color: var(--primary); }
.nav-link.active { font-weight: bold; border-left: 3px solid var(--primary); border-radius: 0 5px 5px 0; }

.tool-card { background: var(--card-bg); 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: 15px; }
label { display: block; font-weight: 600; margin-bottom: 5px; font-size: 0.9em; }
input, select, textarea { width: 100%; padding: 12px; border: 1px solid var(--border); border-radius: 8px; background: var(--input-bg); color: var(--text); font-size: 16px; box-sizing: border-box; }
button { background: var(--primary); color: white; border: none; padding: 14px; border-radius: 8px; font-weight: bold; cursor: pointer; width: 100%; transition: 0.2s; margin-top: 10px; }
button:hover { opacity: 0.9; transform: translateY(-1px); }

/* Timeline for Transit Tool */
.timeline-item { display: flex; gap: 15px; padding: 10px 0; border-left: 2px solid var(--border); margin-left: 10px; padding-left: 20px; position: relative; }
.timeline-item::before { content: ''; position: absolute; left: -6px; top: 15px; width: 10px; height: 10px; border-radius: 50%; background: var(--primary); }
.timeline-time { font-weight: bold; min-width: 80px; font-variant-numeric: tabular-nums; }
.timeline-break::before { background: #f59e0b; }

.result-box { margin-top: 25px; padding: 20px; background: rgba(37,99,235,0.05); border: 1px solid var(--primary); border-radius: 8px; display: none; }
footer { text-align: center; padding: 40px; border-top: 1px solid var(--border); background: var(--card-bg); font-size: 0.9em; margin-top: auto; }
footer a { color: var(--primary); text-decoration: none; margin: 0 10px; }