/* ============================================
   HOMEWORK TRACKER — Clean Dark Theme
   ============================================ */

:root {
  /* Background tones */
  --bg-primary: #121212;
  --bg-secondary: #1e1e1e;
  --bg-card: #1e1e1e;
  --bg-card-hover: #252525;
  --bg-input: #2a2a2a;
  --bg-modal: #1e1e1e;
  --bg-elevated: #2a2a2a;

  /* Borders */
  --border-subtle: #2e2e2e;
  --border-input: #3a3a3a;
  --border-focus: #7c7c7c;

  /* Text */
  --text-primary: #e4e4e4;
  --text-secondary: #a0a0a0;
  --text-muted: #6b6b6b;

  /* Accents — muted, not neon */
  --accent: #7c9cff;
  --accent-bg: rgba(124, 156, 255, 0.1);
  --accent-border: rgba(124, 156, 255, 0.25);
  --green: #5cb87a;
  --green-bg: rgba(92, 184, 122, 0.12);
  --red: #e06060;
  --red-bg: rgba(224, 96, 96, 0.12);
  --orange: #d4a24c;
  --cyan: #5bb8c9;

  /* Spacing */
  --s-xs: 4px;
  --s-sm: 8px;
  --s-md: 16px;
  --s-lg: 24px;
  --s-xl: 32px;

  /* Radius */
  --r-sm: 6px;
  --r-md: 10px;
  --r-lg: 14px;
  --r-full: 9999px;

  --font: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
}

/* ===== RESET ===== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}

body {
  font-family: var(--font);
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
}

.hidden { display: none !important; }
.screen { position: relative; }

/* Scrollbar */
::-webkit-scrollbar { width: 5px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: #333; border-radius: 3px; }

/* ===== BUTTONS ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--s-sm);
  padding: 10px 20px;
  border: none;
  border-radius: var(--r-md);
  font-family: inherit;
  font-size: 0.88rem;
  font-weight: 500;
  cursor: pointer;
  transition: background 0.15s, opacity 0.15s;
}

.btn-primary {
  background: var(--accent);
  color: #111;
}
.btn-primary:hover { opacity: 0.85; }

.btn-ghost {
  background: transparent;
  color: var(--text-secondary);
}
.btn-ghost:hover { background: var(--bg-elevated); color: var(--text-primary); }

.btn-outline {
  background: transparent;
  color: var(--accent);
  border: 1px solid var(--accent-border);
}
.btn-outline:hover { background: var(--accent-bg); }

.btn-danger {
  background: var(--red);
  color: #fff;
}
.btn-danger:hover { opacity: 0.85; }

.btn-icon { padding: 8px; border-radius: var(--r-sm); }
.btn-sm { padding: 6px 14px; font-size: 0.82rem; }
.btn-full { width: 100%; }

/* ===== INPUTS ===== */
input[type="text"],
input[type="password"],
textarea,
select {
  width: 100%;
  padding: 11px 14px;
  background: var(--bg-input);
  border: 1px solid var(--border-input);
  border-radius: var(--r-md);
  color: var(--text-primary);
  font-family: inherit;
  font-size: 0.9rem;
  outline: none;
  transition: border-color 0.15s;
}
input:focus, textarea:focus, select:focus {
  border-color: var(--border-focus);
}
input::placeholder, textarea::placeholder {
  color: var(--text-muted);
}

/* ===== LOGIN ===== */
#login-screen {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  padding: var(--s-lg);
}

.login-container {
  width: 100%;
  max-width: 360px;
  text-align: center;
}

.login-icon {
  font-size: 3.5rem;
  margin-bottom: var(--s-lg);
}

.login-container h1 {
  font-size: 1.6rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: var(--s-xs);
}

.login-subtitle {
  color: var(--text-muted);
  margin-bottom: var(--s-xl);
  font-size: 0.9rem;
}

#login-form {
  display: flex;
  flex-direction: column;
  gap: var(--s-md);
}

.error-text {
  color: var(--red);
  font-size: 0.85rem;
}

/* ===== HEADER ===== */
.app-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--s-lg) var(--s-lg) var(--s-md);
  max-width: 700px;
  margin: 0 auto;
}

.app-title { font-size: 1.4rem; font-weight: 700; }
.header-date { color: var(--text-muted); font-size: 0.84rem; margin-top: 2px; }

/* ===== STATS ===== */
.stats-bar {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--s-sm);
  padding: 0 var(--s-lg);
  max-width: 700px;
  margin: 0 auto var(--s-md);
}

.stat-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--r-md);
  padding: var(--s-md);
  text-align: center;
}

.stat-number {
  display: block;
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--text-primary);
}

.stat-label {
  display: block;
  font-size: 0.7rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-top: 2px;
}

/* ===== FILTERS ===== */
.filter-bar {
  display: flex;
  gap: var(--s-sm);
  padding: 0 var(--s-lg);
  max-width: 700px;
  margin: 0 auto var(--s-lg);
}

.filter-btn {
  padding: 7px 16px;
  border: 1px solid var(--border-subtle);
  border-radius: var(--r-full);
  background: transparent;
  color: var(--text-secondary);
  font-family: inherit;
  font-size: 0.84rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.15s;
}
.filter-btn:hover {
  border-color: #444;
  color: var(--text-primary);
}
.filter-btn.active {
  background: var(--accent);
  border-color: var(--accent);
  color: #111;
}

/* ===== HOMEWORK LIST ===== */
.homework-list {
  max-width: 700px;
  margin: 0 auto;
  padding: 0 var(--s-lg) 100px;
}

.date-group { margin-bottom: var(--s-lg); }

.date-group-header {
  display: flex;
  align-items: center;
  gap: var(--s-sm);
  padding: var(--s-xs) 0;
  margin-bottom: var(--s-sm);
}

.date-group-label {
  font-size: 0.76rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.8px;
  color: var(--text-muted);
  white-space: nowrap;
}
.date-group-label.overdue { color: var(--red); }
.date-group-label.today { color: var(--cyan); }

.date-group-line {
  flex: 1;
  height: 1px;
  background: var(--border-subtle);
}

/* ===== HOMEWORK CARD ===== */
.hw-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--r-lg);
  padding: var(--s-md) var(--s-lg);
  margin-bottom: var(--s-sm);
  transition: background 0.15s, border-color 0.15s;
  animation: slideIn 0.2s ease;
}

@keyframes slideIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

.hw-card:hover {
  border-color: #3a3a3a;
  background: var(--bg-card-hover);
}

.hw-card.completed { opacity: 0.45; }
.hw-card.completed .hw-title {
  text-decoration: line-through;
  color: var(--text-muted);
}

.hw-card-top {
  display: flex;
  align-items: flex-start;
  gap: var(--s-md);
}

/* Checkbox */
.hw-checkbox { flex-shrink: 0; margin-top: 2px; }
.hw-checkbox input[type="checkbox"] { display: none; }
.hw-checkbox label {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 22px;
  height: 22px;
  border: 2px solid #444;
  border-radius: 5px;
  cursor: pointer;
  transition: all 0.15s;
}
.hw-checkbox label:hover { border-color: #666; }
.hw-checkbox input:checked + label {
  background: var(--green);
  border-color: var(--green);
}
.hw-checkbox input:checked + label::after {
  content: '✓';
  color: #fff;
  font-size: 13px;
  font-weight: 700;
}

.hw-content { flex: 1; min-width: 0; }

.hw-title {
  font-size: 0.93rem;
  font-weight: 600;
  margin-bottom: 3px;
}

.hw-meta {
  display: flex;
  align-items: center;
  gap: var(--s-sm);
  flex-wrap: wrap;
}

.hw-subject {
  font-size: 0.76rem;
  font-weight: 500;
  color: var(--accent);
  background: var(--accent-bg);
  padding: 2px 10px;
  border-radius: var(--r-full);
}

.hw-date {
  font-size: 0.76rem;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  gap: 3px;
}
.hw-date.overdue { color: var(--red); font-weight: 500; }
.hw-date.today { color: var(--cyan); font-weight: 500; }
.hw-date.tomorrow { color: var(--orange); }

.hw-description {
  font-size: 0.82rem;
  color: var(--text-secondary);
  margin-top: var(--s-sm);
}

.hw-actions {
  display: flex;
  gap: 2px;
  flex-shrink: 0;
  opacity: 0;
  transition: opacity 0.15s;
}
.hw-card:hover .hw-actions { opacity: 1; }

.hw-action-btn {
  padding: 6px;
  border: none;
  background: transparent;
  color: var(--text-muted);
  cursor: pointer;
  border-radius: var(--r-sm);
  transition: all 0.15s;
  display: flex;
}
.hw-action-btn:hover { background: var(--bg-elevated); color: var(--text-primary); }
.hw-action-btn.delete:hover { color: var(--red); background: var(--red-bg); }

/* ===== PROGRESS BAR ===== */
.hw-progress { margin-top: var(--s-md); }

.progress-header {
  display: flex;
  justify-content: space-between;
  margin-bottom: var(--s-xs);
}

.progress-label { font-size: 0.76rem; color: var(--text-muted); }
.progress-value { font-size: 0.76rem; font-weight: 600; color: var(--text-secondary); }

.progress-bar {
  width: 100%;
  height: 5px;
  background: #2a2a2a;
  border-radius: var(--r-full);
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: var(--accent);
  border-radius: var(--r-full);
  transition: width 0.4s ease;
}

/* ===== SUBTASKS ===== */
.hw-subtasks {
  margin-top: var(--s-sm);
  padding-top: var(--s-sm);
  border-top: 1px solid var(--border-subtle);
}

.subtask-toggle {
  display: flex;
  align-items: center;
  gap: var(--s-xs);
  padding: 4px 0;
  background: none;
  border: none;
  color: var(--text-muted);
  font-family: inherit;
  font-size: 0.8rem;
  cursor: pointer;
}
.subtask-toggle:hover { color: var(--text-secondary); }
.subtask-toggle .arrow {
  transition: transform 0.15s;
  font-size: 0.7rem;
}
.subtask-toggle.open .arrow { transform: rotate(90deg); }

.subtask-list { list-style: none; margin-top: var(--s-sm); }

.subtask-item {
  display: flex;
  align-items: center;
  gap: var(--s-sm);
  padding: 5px 0;
}

.subtask-item .st-checkbox { display: none; }
.subtask-item .st-label {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 18px;
  height: 18px;
  border: 1.5px solid #444;
  border-radius: 4px;
  cursor: pointer;
  transition: all 0.15s;
  flex-shrink: 0;
}
.subtask-item .st-label:hover { border-color: #666; }
.subtask-item .st-checkbox:checked + .st-label {
  background: var(--green);
  border-color: var(--green);
}
.subtask-item .st-checkbox:checked + .st-label::after {
  content: '✓';
  color: #fff;
  font-size: 11px;
  font-weight: 700;
}

.subtask-item .st-title {
  flex: 1;
  font-size: 0.85rem;
  color: var(--text-secondary);
}
.subtask-item .st-checkbox:checked ~ .st-title {
  text-decoration: line-through;
  color: var(--text-muted);
}

.subtask-item .st-delete {
  opacity: 0;
  padding: 2px;
  border: none;
  background: transparent;
  color: var(--text-muted);
  cursor: pointer;
  border-radius: 4px;
  font-size: 0.8rem;
  display: flex;
  transition: all 0.15s;
}
.subtask-item:hover .st-delete { opacity: 1; }
.subtask-item .st-delete:hover { color: var(--red); }

.add-subtask-inline {
  display: flex;
  gap: var(--s-sm);
  margin-top: var(--s-sm);
  padding-top: var(--s-sm);
}
.add-subtask-inline input {
  flex: 1;
  padding: 8px 12px;
  font-size: 0.85rem;
}

/* ===== FAB ===== */
.fab {
  position: fixed;
  bottom: 28px;
  right: 28px;
  width: 56px;
  height: 56px;
  border-radius: 50%;
  border: none;
  background: var(--accent);
  color: #111;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: transform 0.2s, opacity 0.15s;
  z-index: 100;
}
.fab:hover { transform: scale(1.08); opacity: 0.9; }
.fab:active { transform: scale(0.95); }

/* ===== MODAL ===== */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.55);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  padding: var(--s-lg);
  animation: fadeIn 0.15s ease;
}
@keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }

.modal {
  width: 100%;
  max-width: 480px;
  max-height: 85vh;
  overflow-y: auto;
  background: var(--bg-modal);
  border: 1px solid var(--border-subtle);
  border-radius: var(--r-lg);
  padding: var(--s-xl);
  animation: modalSlide 0.2s ease;
}
.modal-sm { max-width: 360px; }

@keyframes modalSlide {
  from { opacity: 0; transform: translateY(12px); }
  to { opacity: 1; transform: translateY(0); }
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--s-lg);
}
.modal-header h2 { font-size: 1.15rem; font-weight: 700; }

.delete-text {
  color: var(--text-secondary);
  margin-bottom: var(--s-lg);
  font-size: 0.9rem;
}

/* ===== FORM ===== */
.form-group { margin-bottom: var(--s-md); }
.form-group label {
  display: block;
  font-size: 0.82rem;
  font-weight: 500;
  color: var(--text-secondary);
  margin-bottom: var(--s-xs);
}

.form-hint {
  display: block;
  font-size: 0.75rem;
  color: var(--text-muted);
  margin-top: 4px;
}

.form-actions {
  display: flex;
  justify-content: flex-end;
  gap: var(--s-sm);
  margin-top: var(--s-lg);
}

.type-toggle {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--s-sm);
}

.type-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--s-sm);
  padding: 11px;
  border: 1px solid var(--border-subtle);
  border-radius: var(--r-md);
  background: transparent;
  color: var(--text-secondary);
  font-family: inherit;
  font-size: 0.85rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.15s;
}
.type-btn:hover { border-color: #444; }
.type-btn.active {
  border-color: var(--accent-border);
  background: var(--accent-bg);
  color: var(--text-primary);
}
.type-icon { font-size: 1.1rem; }

#subtasks-inputs {
  display: flex;
  flex-direction: column;
  gap: var(--s-sm);
  margin-bottom: var(--s-sm);
}

.subtask-input-row {
  display: flex;
  gap: var(--s-sm);
  animation: slideIn 0.15s ease;
}
.subtask-input-row input { flex: 1; padding: 8px 12px; font-size: 0.85rem; }
.subtask-input-row .remove-subtask {
  padding: 8px;
  border: none;
  background: transparent;
  color: var(--text-muted);
  cursor: pointer;
  border-radius: var(--r-sm);
  display: flex;
  align-items: center;
  font-size: 1.1rem;
  transition: color 0.15s;
}
.subtask-input-row .remove-subtask:hover { color: var(--red); }

/* ===== CALENDAR PICKER ===== */
.date-picker-wrapper {
  position: relative;
}

.date-picker-input {
  width: 100%;
  padding: 11px 14px;
  background: var(--bg-input);
  border: 1px solid var(--border-input);
  border-radius: var(--r-md);
  color: var(--text-primary);
  font-family: inherit;
  font-size: 0.9rem;
  cursor: pointer;
  outline: none;
  transition: border-color 0.15s;
  user-select: none;
}
.date-picker-input:focus { border-color: var(--border-focus); }
.date-picker-input.has-value { color: var(--text-primary); }
.date-picker-input.placeholder { color: var(--text-muted); }

.date-picker-clear {
  position: absolute;
  right: 10px;
  top: 50%;
  transform: translateY(-50%);
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 1rem;
  padding: 2px 4px;
  display: none;
}
.date-picker-clear:hover { color: var(--text-primary); }
.date-picker-wrapper.has-value .date-picker-clear { display: block; }

.calendar-dropdown {
  position: absolute;
  top: calc(100% + 6px);
  left: 0;
  z-index: 2000;
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  border-radius: var(--r-md);
  padding: var(--s-md);
  width: 300px;
  animation: fadeIn 0.12s ease;
}

.calendar-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--s-md);
}

.calendar-nav-btn {
  background: none;
  border: none;
  color: var(--text-secondary);
  cursor: pointer;
  padding: 4px 8px;
  border-radius: var(--r-sm);
  font-size: 1rem;
  transition: background 0.12s;
}
.calendar-nav-btn:hover { background: var(--bg-input); color: var(--text-primary); }

.calendar-month-label {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-primary);
}

.calendar-grid {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  gap: 2px;
}

.calendar-weekday {
  text-align: center;
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--text-muted);
  padding: 4px 0 8px;
  text-transform: uppercase;
}

.calendar-day {
  text-align: center;
  padding: 7px 0;
  font-size: 0.84rem;
  border-radius: var(--r-sm);
  cursor: pointer;
  transition: background 0.12s;
  color: var(--text-primary);
  border: none;
  background: none;
  font-family: inherit;
}
.calendar-day:hover { background: var(--bg-input); }
.calendar-day.today {
  border: 1px solid #555;
}
.calendar-day.selected {
  background: var(--accent);
  color: #111;
  font-weight: 600;
}
.calendar-day.other-month {
  color: var(--text-muted);
  opacity: 0.4;
}
.calendar-day.empty {
  cursor: default;
}

.calendar-today-btn {
  display: block;
  width: 100%;
  margin-top: var(--s-sm);
  padding: 6px;
  border: none;
  background: var(--bg-input);
  color: var(--text-secondary);
  font-family: inherit;
  font-size: 0.82rem;
  border-radius: var(--r-sm);
  cursor: pointer;
  transition: background 0.12s;
}
.calendar-today-btn:hover { background: #333; color: var(--text-primary); }

/* ===== EMPTY STATE ===== */
.empty-state {
  text-align: center;
  padding: 60px var(--s-lg);
  max-width: 700px;
  margin: 0 auto;
}
.empty-icon { font-size: 3.5rem; margin-bottom: var(--s-md); }
.empty-state h2 { color: var(--text-secondary); font-size: 1.2rem; margin-bottom: var(--s-sm); }
.empty-state p { color: var(--text-muted); font-size: 0.9rem; }

/* ===== RESPONSIVE ===== */
@media (max-width: 600px) {
  .app-header { padding: var(--s-md) var(--s-md) var(--s-sm); }
  .stats-bar { grid-template-columns: repeat(2, 1fr); padding: 0 var(--s-md); }
  .filter-bar { padding: 0 var(--s-md); }
  .homework-list { padding: 0 var(--s-md) 100px; }
  .hw-actions { opacity: 1; }
  .fab { bottom: 20px; right: 20px; width: 50px; height: 50px; }
  .modal { padding: var(--s-lg); }
  .calendar-dropdown { width: 280px; }
}