/* ===== Reset & Base ===== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background-color: #f0f4f8;
  color: #333;
  min-height: 100vh;
}

/* ===== CSS Variables ===== */
:root {
  --primary: #4a90d9;
  --primary-light: #e8f0fe;
  --bg: #f0f4f8;
  --card-bg: #ffffff;
  --text: #333333;
  --text-secondary: #666666;
  --border: #e0e4e8;
  --priority-high: #e74c3c;
  --priority-medium: #f39c12;
  --priority-low: #27ae60;
  --danger: #e74c3c;
  --radius: 8px;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
}

/* ===== App Container ===== */
#app {
  max-width: 800px;
  margin: 0 auto;
  padding: 20px 16px;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* ===== Header ===== */
.app-header {
  text-align: center;
  padding: 24px 0 20px;
}

.app-title {
  font-size: 28px;
  font-weight: 700;
  color: var(--primary);
  margin-bottom: 4px;
}

.app-subtitle {
  font-size: 14px;
  color: var(--text-secondary);
}

.header-actions {
  display: flex;
  justify-content: center;
  gap: 8px;
  margin-top: 12px;
}

.header-actions button {
  padding: 6px 14px;
  border: 1px solid var(--border);
  background: var(--card-bg);
  border-radius: 6px;
  font-size: 13px;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all 0.2s;
}

.header-actions button:hover {
  background: var(--primary-light);
  color: var(--primary);
  border-color: var(--primary);
}

/* ===== Add Form ===== */
.add-form {
  background: var(--card-bg);
  border-radius: var(--radius);
  padding: 16px;
  margin-bottom: 16px;
  box-shadow: var(--shadow);
}

#todo-form {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.form-input {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 14px;
  font-family: inherit;
  color: var(--text);
  outline: none;
  transition: border-color 0.2s;
}

.form-input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 2px rgba(74, 144, 217, 0.15);
}

.form-textarea {
  resize: vertical;
  min-height: 40px;
}

.form-row {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.form-select {
  flex: 1;
  min-width: 80px;
  padding: 8px 10px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 13px;
  font-family: inherit;
  color: var(--text);
  background: var(--card-bg);
  outline: none;
  cursor: pointer;
}

.form-select:focus {
  border-color: var(--primary);
}

.form-date {
  flex: 1;
  min-width: 120px;
  padding: 8px 10px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 13px;
  font-family: inherit;
  color: var(--text);
  outline: none;
}

.form-date:focus {
  border-color: var(--primary);
}

.btn-add {
  width: 100%;
  padding: 10px;
  background: var(--primary);
  color: #fff;
  border: none;
  border-radius: 6px;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s;
}

.btn-add:hover {
  background: #3a7bc8;
}

.btn-add:active {
  transform: scale(0.98);
}

/* ===== Filter Bar ===== */
.filter-bar {
  margin-bottom: 16px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.filter-tabs {
  display: flex;
  gap: 6px;
}

.filter-btn {
  flex: 1;
  padding: 8px 12px;
  border: 1px solid var(--border);
  background: var(--card-bg);
  border-radius: 6px;
  font-size: 13px;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all 0.2s;
}

.filter-btn:hover {
  background: var(--primary-light);
  color: var(--primary);
}

.filter-btn.active {
  background: var(--primary);
  color: #fff;
  border-color: var(--primary);
}

.filter-tags {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
}

.tag-btn {
  padding: 5px 12px;
  border: 1px solid var(--border);
  background: var(--card-bg);
  border-radius: 20px;
  font-size: 12px;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all 0.2s;
}

.tag-btn:hover {
  background: var(--primary-light);
  color: var(--primary);
}

.tag-btn.active {
  background: var(--primary);
  color: #fff;
  border-color: var(--primary);
}

/* ===== Todo List ===== */
.todo-list {
  display: flex;
  flex-direction: column;
  gap: 8px;
  flex: 1;
}

.todo-item {
  background: var(--card-bg);
  border-radius: var(--radius);
  padding: 12px 14px;
  box-shadow: var(--shadow);
  display: flex;
  align-items: flex-start;
  gap: 10px;
  transition: all 0.2s;
  border-left: 3px solid transparent;
}

.todo-item:hover {
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

/* Priority border colors */
.todo-item.priority-high {
  border-left-color: var(--priority-high);
}

.todo-item.priority-medium {
  border-left-color: var(--priority-medium);
}

.todo-item.priority-low {
  border-left-color: var(--priority-low);
}

/* Overdue items */
.todo-item.overdue {
  opacity: 0.85;
}

.todo-checkbox {
  width: 18px;
  height: 18px;
  margin-top: 2px;
  cursor: pointer;
  accent-color: var(--primary);
  flex-shrink: 0;
}

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

.todo-title {
  font-size: 15px;
  font-weight: 500;
  color: var(--text);
  margin-bottom: 2px;
}

.todo-desc {
  font-size: 13px;
  color: var(--text-secondary);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.todo-meta {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-top: 6px;
  flex-wrap: wrap;
}

.todo-tag {
  font-size: 11px;
  padding: 2px 8px;
  background: var(--primary-light);
  color: var(--primary);
  border-radius: 10px;
  font-weight: 500;
}

.todo-due {
  font-size: 11px;
  color: var(--text-secondary);
}

.priority-badge {
  font-size: 11px;
  padding: 2px 8px;
  border-radius: 10px;
  font-weight: 600;
  color: #fff;
}

.priority-badge.priority-high {
  background: var(--priority-high);
}

.priority-badge.priority-medium {
  background: var(--priority-medium);
}

.priority-badge.priority-low {
  background: var(--priority-low);
}

.btn-delete {
  width: 28px;
  height: 28px;
  border: none;
  background: transparent;
  color: #ccc;
  font-size: 20px;
  cursor: pointer;
  border-radius: 4px;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s;
  flex-shrink: 0;
}

.btn-delete:hover {
  background: #fee;
  color: var(--danger);
}

/* Completed styles */
.todo-item.completed .todo-title {
  text-decoration: line-through;
  color: #aaa;
}

.todo-item.completed .todo-desc {
  color: #bbb;
}

.completed-text {
  text-decoration: line-through;
  color: #aaa;
}

.overdue-text {
  color: var(--priority-high);
  font-weight: 600;
}

/* ===== Empty State ===== */
.empty-state {
  text-align: center;
  padding: 60px 20px;
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.empty-icon {
  font-size: 48px;
  margin-bottom: 12px;
}

.empty-text {
  font-size: 16px;
  color: var(--text-secondary);
  margin-bottom: 4px;
}

.empty-hint {
  font-size: 13px;
  color: #aaa;
}

/* ===== Footer ===== */
.app-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px 0;
  border-top: 1px solid var(--border);
  margin-top: 16px;
}

.todo-count {
  font-size: 13px;
  color: var(--text-secondary);
}

.btn-clear {
  padding: 6px 12px;
  border: 1px solid var(--border);
  background: var(--card-bg);
  border-radius: 6px;
  font-size: 12px;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all 0.2s;
}

.btn-clear:hover {
  background: var(--danger);
  color: #fff;
  border-color: var(--danger);
}

/* ===== Responsive: Desktop >= 768px ===== */
@media (min-width: 768px) {
  #app {
    padding: 30px 24px;
  }

  .app-title {
    font-size: 32px;
  }

  .form-row {
    flex-wrap: nowrap;
  }

  .todo-item {
    padding: 14px 16px;
  }

  .todo-title {
    font-size: 16px;
  }

  .todo-desc {
    white-space: normal;
    overflow: visible;
    text-overflow: unset;
  }
}

/* ===== Responsive: Mobile < 768px ===== */
@media (max-width: 767px) {
  .app-title {
    font-size: 24px;
  }

  .form-row {
    flex-direction: column;
  }

  .form-select,
  .form-date {
    min-width: 100%;
  }

  .todo-meta {
    gap: 6px;
  }

  .app-footer {
    flex-direction: column;
    gap: 10px;
    align-items: flex-start;
  }
}

/* ===== Install Banner ===== */
.install-banner {
  background: linear-gradient(135deg, var(--primary), #3a7bc8);
  color: #fff;
  border-radius: var(--radius);
  padding: 16px 20px;
  margin-bottom: 16px;
  display: none;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  box-shadow: var(--shadow);
}

.install-banner.visible {
  display: flex;
}

.install-banner-text {
  flex: 1;
}

.install-banner-text h3 {
  font-size: 15px;
  font-weight: 600;
  margin-bottom: 2px;
}

.install-banner-text p {
  font-size: 13px;
  opacity: 0.9;
}

.install-banner-close {
  background: rgba(255, 255, 255, 0.2);
  border: none;
  color: #fff;
  font-size: 18px;
  width: 28px;
  height: 28px;
  border-radius: 50%;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 0.2s;
}

.install-banner-close:hover {
  background: rgba(255, 255, 255, 0.35);
}

.install-banner-install {
  padding: 8px 18px;
  background: #fff;
  color: var(--primary);
  border: none;
  border-radius: 6px;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  white-space: nowrap;
  transition: background 0.2s;
}

.install-banner-install:hover {
  background: var(--primary-light);
}

@media (max-width: 767px) {
  .install-banner {
    flex-direction: column;
    text-align: center;
  }

  .install-banner-install {
    width: 100%;
  }
}