:root {
  --bg: #0f172a;
  --surface: #1e293b;
  --surface-2: #334155;
  --text: #f8fafc;
  --muted: #94a3b8;
  --primary: #38bdf8;
  --primary-dark: #0284c7;
  --success: #4ade80;
  --danger: #f87171;
  --radius: 8px;
  --shadow: 0 4px 6px -1px rgba(0,0,0,0.3);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
}

a { color: var(--primary); text-decoration: none; }

.container { max-width: 960px; margin: 0 auto; padding: 1rem; }

.site-header {
  background: var(--surface);
  border-bottom: 1px solid var(--surface-2);
}

.header-content {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.logo { font-size: 1.5rem; font-weight: 700; color: var(--text); }

#main-nav { display: flex; align-items: center; gap: 1rem; }
#main-nav.hidden { display: none; }
#main-nav a { color: var(--muted); }
#main-nav a:hover, #main-nav a.active { color: var(--text); }

.card {
  background: var(--surface);
  border-radius: var(--radius);
  padding: 1.25rem;
  margin-bottom: 1rem;
  box-shadow: var(--shadow);
}

h1, h2, h3 { margin-top: 0; }

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.5rem 1rem;
  border: none;
  border-radius: var(--radius);
  cursor: pointer;
  font-size: 1rem;
  font-weight: 600;
  color: var(--text);
  background: var(--primary-dark);
}

.btn:hover { background: var(--primary); color: #0f172a; }

.btn-secondary { background: var(--surface-2); }

.btn-danger { background: var(--danger); color: #450a0a; }

.form-group { margin-bottom: 1rem; }

label { display: block; margin-bottom: 0.25rem; font-weight: 500; }

input, select, textarea {
  width: 100%;
  padding: 0.5rem;
  border: 1px solid var(--surface-2);
  border-radius: var(--radius);
  background: var(--bg);
  color: var(--text);
  font: inherit;
}

input:focus, select:focus, textarea:focus { outline: 2px solid var(--primary); }

.table-wrap { overflow-x: auto; }

table { width: 100%; border-collapse: collapse; }

th, td { padding: 0.75rem; text-align: left; border-bottom: 1px solid var(--surface-2); }

th { color: var(--muted); font-weight: 600; }

.empty-state { color: var(--muted); text-align: center; padding: 2rem; }

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

.success { color: var(--success); }

.hidden { display: none !important; }

.grid { display: grid; gap: 1rem; }

.grid-2 { grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); }

.set-row { display: grid; grid-template-columns: 1fr 1fr 1fr auto; gap: 0.5rem; align-items: end; }

.exercise-block { border: 1px solid var(--surface-2); border-radius: var(--radius); padding: 1rem; margin-bottom: 1rem; }

.stat { font-size: 2rem; font-weight: 700; color: var(--primary); }

.chart-bar {
  background: var(--primary-dark);
  border-radius: var(--radius);
  min-width: 4px;
  padding: 0.25rem 0.5rem;
  color: var(--text);
  font-size: 0.85rem;
  white-space: nowrap;
}

.auth-form { max-width: 360px; margin: 3rem auto; }

.tabs { display: flex; gap: 1rem; margin-bottom: 1rem; border-bottom: 1px solid var(--surface-2); }

.tab { padding: 0.5rem 0; cursor: pointer; color: var(--muted); }

.tab.active { color: var(--text); border-bottom: 2px solid var(--primary); }

@media (max-width: 600px) {
  .header-content { flex-direction: column; align-items: flex-start; }
  #main-nav { flex-wrap: wrap; }
  .set-row { grid-template-columns: 1fr 1fr; }
}