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

:root {
  --black: #0a0a0a;
  --white: #ffffff;
  --gray-50: #fafafa;
  --gray-100: #f5f5f5;
  --gray-200: #e5e5e5;
  --gray-300: #d4d4d4;
  --gray-400: #a3a3a3;
  --gray-500: #737373;
  --gray-600: #525252;
  --gray-700: #404040;
  --gray-800: #262626;
  --gray-900: #171717;
  --success: #22c55e;
  --danger: #ef4444;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background-color: var(--black);
  color: var(--white);
  line-height: 1.6;
  min-height: 100vh;
}

.hidden {
  display: none !important;
}

/* Typography */
h1, h2, h3, h4 {
  font-weight: 600;
  letter-spacing: -0.02em;
}

/* Buttons */
.btn {
  padding: 0.875rem 1.75rem;
  border: none;
  border-radius: 8px;
  font-size: 0.9375rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s ease;
  letter-spacing: -0.01em;
}

.btn-primary {
  background-color: var(--white);
  color: var(--black);
}

.btn-primary:hover {
  background-color: var(--gray-200);
  transform: translateY(-1px);
}

.btn-danger {
  background-color: transparent;
  color: var(--danger);
  border: 1px solid var(--danger);
}

.btn-danger:hover {
  background-color: var(--danger);
  color: var(--white);
}

.btn-small {
  padding: 0.5rem 1rem;
  font-size: 0.8125rem;
  background-color: transparent;
  color: var(--gray-400);
  border: 1px solid var(--gray-700);
}

.btn-small:hover {
  background-color: var(--gray-800);
  color: var(--white);
  border-color: var(--gray-600);
}

/* Form Elements */
.form-group {
  margin-bottom: 1.25rem;
}

.form-group label {
  display: block;
  margin-bottom: 0.5rem;
  font-weight: 500;
  font-size: 0.875rem;
  color: var(--gray-300);
  letter-spacing: -0.01em;
}

.form-group input,
.form-group select {
  width: 100%;
  padding: 0.875rem 1rem;
  border: 1px solid var(--gray-700);
  border-radius: 8px;
  font-size: 1rem;
  background-color: var(--gray-900);
  color: var(--white);
  transition: all 0.2s ease;
}

.form-group input::placeholder {
  color: var(--gray-600);
}

.form-group input:focus,
.form-group select:focus {
  outline: none;
  border-color: var(--white);
  box-shadow: 0 0 0 3px rgba(255, 255, 255, 0.1);
}

.form-group select {
  cursor: pointer;
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='%23737373' d='M6 8L1 3h10z'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 1rem center;
  padding-right: 2.5rem;
}

.form-group select option {
  background-color: var(--gray-900);
  color: var(--white);
}

.form-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
}

@media (max-width: 600px) {
  .form-row {
    grid-template-columns: 1fr;
  }
}

.error {
  color: var(--danger);
  margin-top: 0.75rem;
  font-size: 0.875rem;
}

.message {
  margin-top: 1rem;
  padding: 0.875rem 1rem;
  border-radius: 8px;
  font-size: 0.875rem;
}

.message.success {
  background-color: rgba(34, 197, 94, 0.1);
  color: var(--success);
  border: 1px solid rgba(34, 197, 94, 0.3);
}

.message.error {
  background-color: rgba(239, 68, 68, 0.1);
  color: var(--danger);
  border: 1px solid rgba(239, 68, 68, 0.3);
}

/* Login Screen */
#login-screen {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: var(--black);
  position: relative;
  overflow: hidden;
}

#login-screen::before {
  content: '';
  position: absolute;
  top: -50%;
  left: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(circle at center, var(--gray-900) 0%, transparent 50%);
  animation: pulse 15s ease-in-out infinite;
}

@keyframes pulse {
  0%, 100% { transform: scale(1); opacity: 0.5; }
  50% { transform: scale(1.1); opacity: 0.3; }
}

.login-container {
  background: var(--gray-900);
  padding: 3rem;
  border-radius: 16px;
  border: 1px solid var(--gray-800);
  width: 100%;
  max-width: 420px;
  margin: 1rem;
  position: relative;
  z-index: 1;
  box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5);
}

.login-container h1 {
  text-align: center;
  color: var(--white);
  margin-bottom: 0.5rem;
  font-size: 1.75rem;
}

.login-container .subtitle {
  text-align: center;
  color: var(--gray-500);
  margin-bottom: 2.5rem;
  font-size: 0.9375rem;
}

.login-container .btn {
  width: 100%;
  margin-top: 0.5rem;
}

/* Dashboard */
header {
  background: var(--gray-900);
  border-bottom: 1px solid var(--gray-800);
  padding: 1.25rem 1.5rem;
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(10px);
}

.header-content {
  max-width: 1000px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.header-content h1 {
  font-size: 1.125rem;
  color: var(--white);
  font-weight: 600;
}

.user-info {
  display: flex;
  align-items: center;
  gap: 1rem;
}

#user-name {
  font-weight: 500;
  color: var(--gray-400);
  font-size: 0.875rem;
}

main {
  max-width: 1000px;
  margin: 0 auto;
  padding: 2rem 1.5rem;
}

/* Stats Section */
.stats-section {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
  margin-bottom: 2rem;
}

@media (max-width: 600px) {
  .stats-section {
    grid-template-columns: 1fr;
  }
}

.stat-card {
  background: var(--gray-900);
  padding: 1.75rem;
  border-radius: 12px;
  text-align: center;
  border: 1px solid var(--gray-800);
  transition: all 0.2s ease;
}

.stat-card:hover {
  border-color: var(--gray-700);
  transform: translateY(-2px);
}

.stat-value {
  display: block;
  font-size: 3rem;
  font-weight: 700;
  color: var(--white);
  line-height: 1;
  margin-bottom: 0.5rem;
  letter-spacing: -0.03em;
}

.stat-label {
  color: var(--gray-500);
  font-size: 0.8125rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-weight: 500;
}

/* Form Section */
.form-section,
.calendar-section,
.list-section {
  background: var(--gray-900);
  padding: 1.75rem;
  border-radius: 12px;
  margin-bottom: 1.5rem;
  border: 1px solid var(--gray-800);
}

.form-section h2,
.calendar-section h2,
.list-section h2 {
  margin-bottom: 1.5rem;
  color: var(--white);
  font-size: 1.125rem;
  font-weight: 600;
}

/* Calendar */
.calendar-header {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  text-align: center;
  font-weight: 600;
  color: var(--gray-500);
  font-size: 0.75rem;
  margin-bottom: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.calendar-grid {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  gap: 6px;
}

.calendar-day {
  aspect-ratio: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 8px;
  font-size: 0.875rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s ease;
  position: relative;
  background-color: var(--gray-800);
  color: var(--gray-400);
}

.calendar-day:hover {
  background-color: var(--gray-700);
  color: var(--white);
}

.calendar-day.empty {
  background-color: transparent;
  cursor: default;
}

.calendar-day.empty:hover {
  background-color: transparent;
}

.calendar-day.exercised {
  background-color: var(--white);
  color: var(--black);
  font-weight: 600;
}

.calendar-day.exercised:hover {
  background-color: var(--gray-200);
}

.calendar-day.rest {
  background-color: var(--gray-800);
  color: var(--gray-500);
  border: 1px dashed var(--gray-700);
}

.calendar-day.today {
  box-shadow: inset 0 0 0 2px var(--success);
}

/* Workout List */
.workout-list {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.workout-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1.25rem;
  background-color: var(--gray-800);
  border-radius: 10px;
  cursor: pointer;
  transition: all 0.2s ease;
  border: 1px solid transparent;
}

.workout-item:hover {
  background-color: var(--gray-700);
  border-color: var(--gray-600);
  transform: translateX(4px);
}

.workout-item.exercised {
  border-left: 3px solid var(--white);
}

.workout-item.rest {
  border-left: 3px solid var(--gray-600);
}

.workout-info h4 {
  font-size: 0.9375rem;
  margin-bottom: 0.25rem;
  color: var(--white);
  font-weight: 500;
}

.workout-info p {
  font-size: 0.8125rem;
  color: var(--gray-500);
}

.workout-badge {
  padding: 0.375rem 0.875rem;
  border-radius: 9999px;
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

.workout-badge.exercised {
  background-color: var(--white);
  color: var(--black);
}

.workout-badge.rest {
  background-color: var(--gray-700);
  color: var(--gray-400);
}

.empty-state {
  text-align: center;
  padding: 3rem 2rem;
  color: var(--gray-500);
  font-size: 0.9375rem;
}

/* Leaderboard */
.leaderboard-section {
  background: var(--gray-900);
  padding: 1.75rem;
  border-radius: 12px;
  margin-bottom: 1.5rem;
  border: 1px solid var(--gray-800);
}

.leaderboard-section h2 {
  margin-bottom: 1.5rem;
  color: var(--white);
  font-size: 1.125rem;
  font-weight: 600;
}

.leaderboard {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.leaderboard-item {
  display: flex;
  align-items: center;
  padding: 1rem 1.25rem;
  background-color: var(--gray-800);
  border-radius: 10px;
  transition: all 0.2s ease;
  border: 1px solid transparent;
}

.leaderboard-item:hover {
  background-color: var(--gray-700);
  border-color: var(--gray-600);
}

.leaderboard-item.current-user {
  border: 1px solid var(--white);
  background-color: var(--gray-800);
}

.leaderboard-item.first-place {
  background: linear-gradient(135deg, var(--gray-800) 0%, var(--gray-700) 100%);
}

.leaderboard-rank {
  font-size: 1.25rem;
  font-weight: 700;
  width: 2.5rem;
  color: var(--gray-400);
}

.leaderboard-item.first-place .leaderboard-rank {
  color: var(--white);
}

.leaderboard-info {
  flex: 1;
  margin-left: 0.75rem;
}

.leaderboard-name {
  font-weight: 600;
  color: var(--white);
  font-size: 0.9375rem;
  margin-bottom: 0.125rem;
}

.leaderboard-details {
  font-size: 0.8125rem;
  color: var(--gray-500);
}

.leaderboard-stats {
  display: flex;
  gap: 1.5rem;
  text-align: right;
}

.leaderboard-stat {
  display: flex;
  flex-direction: column;
}

.leaderboard-stat-value {
  font-size: 1.125rem;
  font-weight: 600;
  color: var(--white);
}

.leaderboard-stat-label {
  font-size: 0.6875rem;
  color: var(--gray-500);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

@media (max-width: 600px) {
  .leaderboard-stats {
    gap: 1rem;
  }

  .leaderboard-stat-value {
    font-size: 1rem;
  }
}

/* Modal */
.modal {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(0, 0, 0, 0.8);
  backdrop-filter: blur(4px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
}

.modal-content {
  background: var(--gray-900);
  padding: 2rem;
  border-radius: 16px;
  max-width: 400px;
  width: 90%;
  position: relative;
  border: 1px solid var(--gray-800);
  box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5);
}

.modal-close {
  position: absolute;
  top: 1.25rem;
  right: 1.25rem;
  font-size: 1.5rem;
  cursor: pointer;
  color: var(--gray-500);
  transition: color 0.2s ease;
  line-height: 1;
}

.modal-close:hover {
  color: var(--white);
}

#modal-date {
  margin-bottom: 1.25rem;
  color: var(--white);
  font-size: 1.125rem;
  font-weight: 600;
  padding-right: 2rem;
}

#modal-body {
  margin-bottom: 1.75rem;
}

#modal-body p {
  margin-bottom: 0.625rem;
  color: var(--gray-400);
  font-size: 0.9375rem;
}

#modal-body strong {
  color: var(--gray-300);
  font-weight: 500;
}

/* Scrollbar */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: var(--gray-900);
}

::-webkit-scrollbar-thumb {
  background: var(--gray-700);
  border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
  background: var(--gray-600);
}

/* Selection */
::selection {
  background-color: var(--white);
  color: var(--black);
}