:root {
    --bg: #f5f5f5;
    --bg-card: #fff;
    --text: #333;
    --text-secondary: #666;
    --nav-bg: #1a1a2e;
    --nav-text: #fff;
    --nav-link: #ccc;
    --border: #ccc;
    --border-table: #eee;
    --btn-bg: #1a1a2e;
    --btn-hover: #16213e;
    --btn-text: #fff;
    --danger: #c0392b;
    --danger-hover: #a93226;
    --primary: #2980b9;
    --success: #27ae60;
    --goal-bg: #d4edda;
    --goal-border: #27ae60;
    --goal-text: #155724;
    --chart-shadow: rgba(0,0,0,0.1);
    --chart-card-bg: #f8f9fa;
    --chart-card-text: #333;
    --chart-card-dim: #888;
    --chart-grid: rgba(0,0,0,0.06);
    --chart-tick: rgba(0,0,0,0.45);
    --chart-border: rgba(0,0,0,0.08);
    --chart-tooltip-bg: rgba(255,255,255,0.95);
    --chart-tooltip-border: rgba(0,0,0,0.1);
    --chart-tooltip-text: #333;
    --chart-tooltip-dim: #888;
}

body.dark-mode {
    --bg: #121212;
    --bg-card: #1e1e1e;
    --text: #e0e0e0;
    --text-secondary: #999;
    --nav-bg: #0d0d1a;
    --nav-text: #fff;
    --nav-link: #aaa;
    --border: #444;
    --border-table: #333;
    --btn-bg: #2a2a4a;
    --btn-hover: #3a3a5a;
    --btn-text: #fff;
    --danger: #e74c3c;
    --danger-hover: #c0392b;
    --primary: #5dade2;
    --success: #2ecc71;
    --goal-bg: #1a3a2a;
    --goal-border: #27ae60;
    --goal-text: #6fcf97;
    --chart-shadow: rgba(0,0,0,0.4);
    --chart-card-bg: #0E2630;
    --chart-card-text: #e6edf3;
    --chart-card-dim: rgba(255,255,255,0.5);
    --chart-grid: rgba(255,255,255,0.04);
    --chart-tick: rgba(255,255,255,0.35);
    --chart-border: rgba(255,255,255,0.08);
    --chart-tooltip-bg: rgba(10,14,20,0.88);
    --chart-tooltip-border: rgba(255,255,255,0.08);
    --chart-tooltip-text: #fff;
    --chart-tooltip-dim: rgba(255,255,255,0.5);
}

* { box-sizing: border-box; margin: 0; padding: 0; }
body { font-family: system-ui, sans-serif; background: var(--bg); color: var(--text); }
nav { background: var(--nav-bg); color: var(--nav-text); padding: 1rem 2rem; display: flex; align-items: center; gap: 1.5rem; }
nav a { color: var(--nav-link); text-decoration: none; }
nav a:hover { color: var(--nav-text); }
.nav-right { margin-left: auto; display: flex; align-items: center; gap: 1rem; }
main { max-width: 960px; margin: 2rem auto; padding: 0 1rem; }
h2 { margin-bottom: 1rem; }
h3 { margin-bottom: 0.5rem; }
.chart-container {
    background: var(--chart-card-bg);
    padding: 24px 24px 16px;
    border-radius: 14px;
    margin-bottom: 2rem;
    box-shadow: 0 1px 3px var(--chart-shadow), 0 0 40px rgba(0,0,0,0.02);
    border: 1px solid var(--chart-border);
    transition: background 0.2s ease, border-color 0.2s ease;
}
.chart-wrap { position: relative; height: 300px; }
.chart-container canvas { cursor: crosshair; width: 100% !important; }
.recent { display: grid; grid-template-columns: 1fr 1fr; gap: 1.5rem; }
.recent > div { background: var(--bg-card); padding: 1rem; border-radius: 8px; box-shadow: 0 1px 3px var(--chart-shadow); }
table { width: 100%; border-collapse: collapse; }
th, td { padding: 0.5rem; text-align: left; border-bottom: 1px solid var(--border-table); }
th { font-weight: 600; }
.form-card { background: var(--bg-card); padding: 1.5rem; border-radius: 8px; box-shadow: 0 1px 3px var(--chart-shadow); max-width: 480px; }
label { display: block; margin-bottom: 1rem; font-weight: 500; }
input, textarea, select { display: block; width: 100%; margin-top: 0.25rem; padding: 0.5rem; border: 1px solid var(--border); border-radius: 4px; background: var(--bg-card); color: var(--text); }
button, .btn { background: var(--btn-bg); color: var(--btn-text); border: none; padding: 0.6rem 1.2rem; border-radius: 4px; cursor: pointer; text-decoration: none; display: inline-block; margin-top: 0.5rem; }
button:hover, .btn:hover { background: var(--btn-hover); }
.btn-danger { background: var(--danger); margin-left: 0.5rem; }
.btn-danger:hover { background: var(--danger-hover); }
.btn-small { padding: 0.25rem 0.6rem; font-size: 0.8rem; margin-top: 0; }
.actions { white-space: nowrap; }
.actions form { display: inline; }
.actions .btn-small { margin-left: 0.25rem; }
.error { color: var(--danger); margin-bottom: 1rem; }
.login-body { display: flex; justify-content: center; align-items: center; min-height: 100vh; }
.login-card { background: var(--bg-card); padding: 2rem; border-radius: 8px; box-shadow: 0 2px 10px var(--chart-shadow); width: 320px; }
.login-card h1 { text-align: center; margin-bottom: 1.5rem; }
.datetime-row { display: flex; gap: 0.75rem; }
.datetime-row input { flex: 1; min-width: 0; }
.goal-banner { background: var(--goal-bg); border: 1px solid var(--goal-border); color: var(--goal-text); padding: 0.75rem 1rem; border-radius: 8px; margin-bottom: 1.5rem; display: flex; align-items: center; gap: 0.5rem; font-size: 0.95rem; }
.goal-banner a { color: var(--goal-text); font-weight: 600; margin-left: auto; }
.stats-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(160px, 1fr)); gap: 1rem; margin-bottom: 1.5rem; }
.stat-card { background: var(--bg-card); padding: 1rem; border-radius: 8px; box-shadow: 0 1px 3px var(--chart-shadow); text-align: center; }
.stat-value { font-size: 1.5rem; font-weight: 700; color: var(--text); }
.stat-label { font-size: 0.85rem; color: var(--text-secondary); margin-top: 0.25rem; }
.latest-weight-card {
    background: var(--bg-card);
    padding: 1rem;
    border-radius: 8px;
    box-shadow: 0 1px 3px var(--chart-shadow);
    text-align: center;
    max-width: 480px;
    margin-bottom: 1.5rem;
}
.latest-weight-meta {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-top: 0.5rem;
}
.latest-weight-notes {
    font-size: 0.85rem;
    color: var(--text-secondary);
    font-style: italic;
    margin-top: 0.5rem;
    padding-top: 0.5rem;
    border-top: 1px solid var(--border-table);
}
.settings-form { background: var(--bg-card); padding: 1.5rem; border-radius: 8px; box-shadow: 0 1px 3px var(--chart-shadow); max-width: 480px; }
.help-text { color: var(--text-secondary); font-size: 0.85rem; margin-top: 0.25rem; }
.theme-toggle { display: flex; justify-content: center; align-items: center; gap: 0.75rem; padding: 1.5rem 0 2rem; font-size: 0.9rem; color: var(--text-secondary); }
.theme-toggle button { background: none; border: 1px solid var(--border); color: var(--text-secondary); padding: 0.4rem 0.8rem; border-radius: 4px; cursor: pointer; font-size: 0.85rem; }
.theme-toggle button:hover { background: var(--bg-card); color: var(--text); }
.theme-toggle button.active { background: var(--btn-bg); color: var(--btn-text); border-color: var(--btn-bg); }
@media (max-width: 600px) { .recent { grid-template-columns: 1fr; } .stats-grid { grid-template-columns: 1fr 1fr; } }