:root {
  color-scheme: light;
  --color-bg: #f4f5f7;
  --color-surface: #ffffff;
  --color-text: #1f2933;
  --color-muted: #6b7280;
  --color-border: #d1d5db;
  --color-primary: #2563eb;
  --color-primary-contrast: #ffffff;
  --color-focus: #2563eb;
  --radius: 8px;
  --spacing-1: 4px;
  --spacing-2: 8px;
  --spacing-3: 16px;
  --spacing-4: 24px;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
}

body {
  min-height: 100vh;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  color: var(--color-text);
  background-color: var(--color-bg);
  line-height: 1.5;
  overflow-x: hidden;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.app-header {
  padding: var(--spacing-4) var(--spacing-3) var(--spacing-2);
  text-align: center;
}

.app-header h1 {
  margin: 0;
  font-size: 1.75rem;
}

.app-tagline {
  margin: var(--spacing-1) 0 0;
  color: var(--color-muted);
  font-size: 0.95rem;
}

.app-main {
  width: 100%;
  max-width: 640px;
  margin: 0 auto;
  padding: 0 var(--spacing-3) var(--spacing-4);
}

.add-form {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-2);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: var(--spacing-3);
  margin-bottom: var(--spacing-3);
}

.add-form__field {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-1);
}

.add-form__field label {
  font-weight: 600;
  font-size: 0.9rem;
}

.add-form__field input {
  width: 100%;
  padding: var(--spacing-2);
  font-size: 1rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-surface);
  color: var(--color-text);
}

.add-form__submit {
  align-self: flex-end;
  padding: var(--spacing-2) var(--spacing-4);
  font-size: 1rem;
  font-weight: 600;
  color: var(--color-primary-contrast);
  background-color: var(--color-primary);
  border: none;
  border-radius: var(--radius);
  cursor: pointer;
}

.add-form__submit:hover {
  filter: brightness(0.95);
}

.add-form__field select {
  width: 100%;
  padding: var(--spacing-2);
  font-size: 1rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-surface);
  color: var(--color-text);
}

.add-form__new-group {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-1);
  padding-top: var(--spacing-2);
  border-top: 1px solid var(--color-border);
}

.add-form__new-group label {
  font-weight: 600;
  font-size: 0.9rem;
}

.add-form__new-group-row {
  display: flex;
  gap: var(--spacing-2);
}

.add-form__new-group-row input {
  flex: 1;
  padding: var(--spacing-2);
  font-size: 1rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-surface);
  color: var(--color-text);
}

.add-form__group-submit {
  padding: var(--spacing-2) var(--spacing-3);
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--color-text);
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  cursor: pointer;
}

.add-form__group-submit:hover {
  filter: brightness(0.97);
}

.add-form__field input:focus-visible,
.add-form__field select:focus-visible,
.add-form__submit:focus-visible,
.add-form__group-submit:focus-visible,
.add-form__new-group-row input:focus-visible {
  outline: 3px solid var(--color-focus);
  outline-offset: 2px;
}

.task-list-section {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: var(--spacing-3);
}

.task-toolbar {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-2);
  margin-bottom: var(--spacing-3);
}

.task-filters {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-1);
}

.task-filters__btn {
  padding: var(--spacing-1) var(--spacing-3);
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--color-text);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  cursor: pointer;
}

.task-filters__btn:hover {
  filter: brightness(0.97);
}

.task-filters__btn:focus-visible {
  outline: 3px solid var(--color-focus);
  outline-offset: 2px;
}

.task-filters__btn[aria-pressed="true"] {
  color: var(--color-primary-contrast);
  background-color: var(--color-primary);
  border-color: var(--color-primary);
}

.task-counter {
  margin: 0;
  color: var(--color-muted);
  font-size: 0.9rem;
}

.task-list {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-3);
}

.task-group {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-2);
}

.task-group__title {
  margin: 0;
  font-size: 1rem;
  color: var(--color-muted);
}

.task-group__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: var(--spacing-2);
}

.task-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--spacing-2);
  padding: var(--spacing-2);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
}

.task-item__checkbox {
  flex-shrink: 0;
  width: 18px;
  height: 18px;
  cursor: pointer;
}

.task-item__checkbox:focus-visible {
  outline: 3px solid var(--color-focus);
  outline-offset: 2px;
}

.task-item__text {
  flex: 1;
  overflow-wrap: anywhere;
  cursor: pointer;
}

.task-item--completed .task-item__text {
  color: var(--color-muted);
  text-decoration: line-through;
}

.task-item__delete {
  flex-shrink: 0;
  padding: var(--spacing-1) var(--spacing-2);
  font-size: 0.85rem;
  font-weight: 600;
  color: #b91c1c;
  background: transparent;
  border: 1px solid #b91c1c;
  border-radius: var(--radius);
  cursor: pointer;
}

.task-item__delete:hover {
  background-color: #fee2e2;
}

.task-item__delete:focus-visible {
  outline: 3px solid var(--color-focus);
  outline-offset: 2px;
}

.empty-state {
  margin: 0;
  padding: var(--spacing-3) 0;
  color: var(--color-muted);
  text-align: center;
}

.app-footer {
  display: flex;
  justify-content: center;
  padding: var(--spacing-3);
}

.app-footer__badge {
  margin: 0;
  padding: var(--spacing-1) var(--spacing-3);
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--color-primary-contrast);
  background-color: var(--color-primary);
  border-radius: var(--radius);
}

@media (min-width: 640px) {
  .add-form {
    flex-direction: row;
    flex-wrap: wrap;
    align-items: flex-end;
  }

  .add-form__field {
    flex: 1;
  }

  .add-form__submit {
    align-self: flex-end;
  }

  .add-form__new-group {
    flex-basis: 100%;
    border-top: 1px solid var(--color-border);
  }

  .task-toolbar {
    flex-direction: row;
    align-items: center;
    justify-content: space-between;
  }
}