:root {
  --bg: #f8f9fa;
  --accent: #0066cc;
  --accent-dark: #0052a3;
  --text: #1a1a1a;
  --text-secondary: #666666;
  --card-bg: #ffffff;
  --border: #e0e0e0;
  --success: #00b366;
  --danger: #cc0000;
  --warning: #ff9900;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html, body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', sans-serif;
  background-color: var(--bg);
  color: var(--text);
  line-height: 1.6;
  letter-spacing: 0.3px;
}

h1 {
  font-size: 2.5rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
  background: linear-gradient(135deg, var(--accent) 0%, #0052a3 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

h2 {
  font-size: 1.8rem;
  font-weight: 600;
  margin-bottom: 1rem;
  color: var(--accent);
}

h3 {
  font-size: 1.3rem;
  font-weight: 500;
  margin-bottom: 0.8rem;
  color: var(--text);
}

p {
  color: var(--text-secondary);
  margin-bottom: 1rem;
}

body {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  width: 100%;
  padding: 0 20px;
}

header {
  background: linear-gradient(180deg, var(--card-bg) 0%, transparent 100%);
  border-bottom: 1px solid var(--border);
  padding: 1.5rem 0;
  position: sticky;
  top: 0;
  z-index: 100;
}

nav {
  display: flex;
  gap: 2rem;
  align-items: center;
}

nav a {
  color: var(--text-secondary);
  text-decoration: none;
  font-weight: 500;
  transition: all 0.3s ease;
  padding: 0.5rem 1rem;
  border-radius: 6px;
}

nav a:hover,
nav a.active {
  color: var(--accent);
  background: rgba(0, 102, 204, 0.1);
}

main {
  flex: 1;
  padding: 2rem 0;
}

.card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.5rem;
  transition: all 0.3s ease;
  margin-bottom: 1.5rem;
}

.card:hover {
  border-color: var(--accent);
  box-shadow: 0 4px 12px rgba(0, 102, 204, 0.1);
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 1.5rem;
  margin-bottom: 2rem;
}

.stat-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.5rem;
  text-align: center;
  transition: all 0.3s ease;
}

.stat-card:hover {
  border-color: var(--accent);
  box-shadow: 0 4px 12px rgba(0, 102, 204, 0.1);
}

.stat-label {
  color: var(--text-secondary);
  font-size: 0.9rem;
  margin-bottom: 0.5rem;
  text-transform: uppercase;
  letter-spacing: 1px;
}

.stat-value {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--accent);
  margin-bottom: 0.5rem;
}

.stat-change {
  font-size: 0.9rem;
  padding: 0.25rem 0.75rem;
  border-radius: 4px;
  display: inline-block;
}

.stat-change.positive {
  background: rgba(0, 179, 102, 0.2);
  color: var(--success);
}

.stat-change.negative {
  background: rgba(204, 0, 0, 0.2);
  color: var(--danger);
}

.form-group {
  margin-bottom: 1.5rem;
}

label {
  display: block;
  margin-bottom: 0.5rem;
  font-weight: 500;
  color: var(--text);
}

input[type="text"],
input[type="date"],
input[type="number"],
select,
textarea {
  width: 100%;
  padding: 0.75rem;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--text);
  font-size: 1rem;
  transition: all 0.3s ease;
  font-family: inherit;
}

input[type="text"]:focus,
input[type="date"]:focus,
input[type="number"]:focus,
select:focus,
textarea:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 10px rgba(0, 102, 204, 0.2);
}

textarea {
  resize: vertical;
  min-height: 80px;
}

button,
.btn {
  padding: 0.75rem 1.5rem;
  background: linear-gradient(135deg, var(--accent) 0%, var(--accent-dark) 100%);
  color: white;
  border: none;
  border-radius: 6px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.3s ease;
  font-size: 1rem;
  text-decoration: none;
  display: inline-block;
}

button:hover,
.btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 20px rgba(0, 102, 204, 0.3);
}

button:active {
  transform: translateY(0);
}

button.secondary {
  background: transparent;
  color: var(--accent);
  border: 1px solid var(--accent);
}

button.secondary:hover {
  background: rgba(0, 102, 204, 0.1);
}

button.danger {
  background: linear-gradient(135deg, var(--danger) 0%, #990000 100%);
}

button:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

.exercise-item {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1.25rem;
  margin-bottom: 1rem;
}

.exercise-item header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  border: none;
  padding: 0;
}

.exercise-name {
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--accent);
}

.exercise-muscles {
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-top: 0.25rem;
}

.sets-summary {
  margin-top: 0.75rem;
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.set-row {
  display: flex;
  gap: 1rem;
  margin-bottom: 1rem;
  align-items: center;
}

.set-input-group {
  flex: 1;
  display: flex;
  gap: 0.5rem;
  align-items: center;
}

.set-input-group label {
  margin: 0;
  min-width: 40px;
  font-weight: 500;
}

.set-input-group input {
  width: 70px;
  padding: 0.5rem;
  font-size: 0.9rem;
}

.remove-btn {
  padding: 0.5rem 0.75rem;
  background: var(--danger);
  color: white;
  border: none;
  border-radius: 4px;
  cursor: pointer;
  font-size: 0.9rem;
}

.remove-btn:hover {
  background: #990000;
}

.chart-container {
  position: relative;
  height: 400px;
  margin-bottom: 2rem;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.5rem;
}

.session {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  margin-bottom: 1.5rem;
  overflow: hidden;
}

.session-header {
  background: rgba(0, 102, 204, 0.05);
  border-bottom: 1px solid var(--border);
  padding: 1rem 1.5rem;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: background 0.3s ease;
}

.session-header:hover {
  background: rgba(0, 102, 204, 0.1);
}

.session-date {
  font-weight: 600;
  font-size: 1.1rem;
  color: var(--accent);
}

.session-meta {
  display: flex;
  gap: 2rem;
  font-size: 0.9rem;
  margin-top: 0.5rem;
}

.session-meta span {
  color: var(--text-secondary);
}

.session-body {
  padding: 1.5rem;
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease;
}

.session.expanded .session-body {
  max-height: 2000px;
}

.exercise-in-session {
  margin-bottom: 1.5rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--border);
}

.exercise-in-session:last-child {
  margin-bottom: 0;
  padding-bottom: 0;
  border-bottom: none;
}

select {
  width: 100%;
  max-width: 300px;
}

table {
  width: 100%;
  border-collapse: collapse;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  overflow: hidden;
}

th {
  background: rgba(0, 102, 204, 0.1);
  padding: 1rem;
  text-align: left;
  font-weight: 600;
  color: var(--accent);
  border-bottom: 1px solid var(--border);
}

td {
  padding: 1rem;
  border-bottom: 1px solid var(--border);
}

tr:last-child td {
  border-bottom: none;
}

tr:hover {
  background: rgba(0, 102, 204, 0.05);
}

.text-center {
  text-align: center;
}

.text-secondary {
  color: var(--text-secondary);
}

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

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

.mt-1 { margin-top: 0.5rem; }
.mt-2 { margin-top: 1rem; }
.mt-3 { margin-top: 1.5rem; }
.mb-1 { margin-bottom: 0.5rem; }
.mb-2 { margin-bottom: 1rem; }
.mb-3 { margin-bottom: 1.5rem; }
.gap-1 { gap: 0.5rem; }
.gap-2 { gap: 1rem; }
.gap-3 { gap: 1.5rem; }

.spinner {
  border: 3px solid var(--border);
  border-top: 3px solid var(--accent);
  border-radius: 50%;
  width: 30px;
  height: 30px;
  animation: spin 1s linear infinite;
  display: inline-block;
}

@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

@media (max-width: 768px) {
  .container { padding: 1rem; }
  h1 { font-size: 1.8rem; margin-bottom: 0.75rem; }
  h2 { font-size: 1.3rem; margin-bottom: 0.75rem; }
  h3 { font-size: 1.1rem; }

  nav { flex-wrap: wrap; gap: 0.5rem; }
  nav a { padding: 0.5rem 0.75rem; font-size: 0.9rem; }

  .card-grid { grid-template-columns: 1fr; gap: 1rem; }
  .card { padding: 1rem; margin-bottom: 1rem; }

  .chart-container { height: 300px; padding: 0.75rem; margin-bottom: 1.5rem; }

  .session-meta { flex-direction: column; gap: 0.5rem; }
  .set-row { flex-direction: column; gap: 0.75rem; }

  .btn { padding: 0.75rem 1rem; min-height: 44px; font-size: 1rem; }

  input, select, textarea { padding: 0.75rem; font-size: 1rem; }

  .form-group { margin-bottom: 1.5rem; }
}

/* Tooltips */
.tip-wrap {
  position: relative;
  display: inline-flex;
  align-items: center;
}
.tip-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--border);
  color: var(--text-secondary);
  font-size: 0.7rem;
  font-weight: 700;
  cursor: pointer;
  user-select: none;
  flex-shrink: 0;
  transition: background 0.15s;
}
.tip-icon:hover { background: var(--accent); color: #fff; }
.tip-box {
  display: none;
  position: absolute;
  top: calc(100% + 6px);
  left: 0;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.6rem 0.8rem;
  font-size: 0.85rem;
  color: var(--text);
  line-height: 1.5;
  width: 240px;
  z-index: 200;
  box-shadow: 0 4px 16px rgba(0,0,0,0.4);
  white-space: normal;
  pointer-events: none;
}
.tip-wrap:hover .tip-box,
.tip-wrap.open .tip-box { display: block; }

@media (max-width: 600px) {
  .exercise-sets-row { flex-direction: column !important; gap: 0.5rem !important; }
  .exercise-sets-row ul { padding-left: 1rem; }
}

@media (max-width: 480px) {
  .container { padding: 0.75rem; }
  h1 { font-size: 1.2rem; margin-bottom: 0.5rem !important; }
  h2 { font-size: 1.1rem; }
  .card { padding: 0.75rem; }
  .chart-container { height: 250px; padding: 0.5rem; margin-bottom: 1rem; }

  header { padding: 0.75rem 0.5rem; background: var(--card-bg) !important; }
  nav { flex-direction: column; gap: 0.5rem; align-items: stretch; }
  nav a { padding: 0.5rem; text-align: center; font-size: 0.9rem; }

  main { margin-top: 0.5rem; }
  footer { padding: 1rem; font-size: 0.85rem; }
}

footer {
  text-align: center;
  padding: 2rem;
  color: var(--text-secondary);
  border-top: 1px solid var(--border);
  margin-top: 3rem;
}