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

:root {
  /* Neobrutalism Color Palette */
  --color-bg: #ffffff;
  --color-surface: #ffffff;
  --color-accent-yellow: #FFFF00;
  --color-accent-pink: #FF1493;
  --color-text: #000000;
  --color-text-muted: #999999;
  --color-border: #000000;
  --color-disabled: #E0E0E0;
  --color-completed-text: #999999;
  
  /* Neobrutalism Styling */
  --border-width: 4px;
  --border-width-sm: 3px;
  --shadow-hard: 4px 4px 0px #000000;
  --shadow-hard-sm: 3px 3px 0px #000000;
  --shadow-hard-xs: 2px 2px 0px #000000;
  --radius: 0;
  --transition: 50ms linear;
}

/* ============================================================
   Utility Classes
   ============================================================ */

/* Hidden utility — used to show/hide elements via JS */
.hidden {
  display: none !important;
}

/* Screen-reader only — visually hidden but accessible */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* ============================================================
   Layout
   ============================================================ */
body {
  background-color: var(--color-bg);
  color: var(--color-text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  font-size: 16px;
  line-height: 1.5;
  min-height: 100vh;
  padding: 24px 16px 48px;
}

#app {
  background-color: var(--color-surface);
  border-radius: var(--radius);
  margin: 0 auto;
  max-width: 600px;
  padding: 0;
}

/* ============================================================
   Header
   ============================================================ */
header {
  background: var(--color-surface);
  border-bottom: var(--border-width) solid var(--color-border);
  padding: 20px;
  text-align: center;
}

header h1 {
  color: var(--color-text);
  font-size: 36px;
  font-weight: bold;
  letter-spacing: 2px;
  line-height: 1.2;
  text-transform: uppercase;
  margin: 0;
}

/* ============================================================
   Input Section
   ============================================================ */
#input-section {
  padding: 20px;
  background: var(--color-surface);
}

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

#task-input {
  flex: 1;
  padding: 12px;
  font-size: 16px;
  border: var(--border-width) solid var(--color-border);
  background: var(--color-surface);
  color: var(--color-text);
  box-shadow: var(--shadow-hard);
  transition: transform var(--transition), box-shadow var(--transition);
}

#task-input::placeholder {
  color: var(--color-text-muted);
}

#task-input:focus {
  outline: none;
  transform: translate(2px, 2px);
  box-shadow: 2px 2px 0px var(--color-border);
}

#task-input:focus-visible {
  outline: none;
  transform: translate(2px, 2px);
  box-shadow: 2px 2px 0px var(--color-border);
}

#add-btn {
  padding: 12px 24px;
  font-size: 16px;
  font-weight: bold;
  background-color: var(--color-accent-yellow);
  color: var(--color-text);
  border: var(--border-width) solid var(--color-border);
  box-shadow: var(--shadow-hard);
  cursor: pointer;
  text-transform: uppercase;
  transition: transform var(--transition), box-shadow var(--transition);
  white-space: nowrap;
}

#add-btn:hover {
  transform: translate(2px, 2px);
  box-shadow: 2px 2px 0px var(--color-border);
}

#add-btn:active {
  transform: translate(4px, 4px);
  box-shadow: 0px 0px 0px var(--color-border);
}

#add-btn:focus-visible {
  outline: none;
  transform: translate(2px, 2px);
  box-shadow: 2px 2px 0px var(--color-border);
}

/* ============================================================
   Error Message (inline validation)
   ============================================================ */
#error-msg {
  background-color: #FFE6E6;
  border: var(--border-width-sm) solid var(--color-accent-pink);
  color: var(--color-accent-pink);
  font-size: 14px;
  font-weight: bold;
  margin-top: 8px;
  padding: 12px;
  box-shadow: var(--shadow-hard-xs);
  display: flex;
  align-items: center;
  gap: 8px;
}

#error-msg::before {
  content: '⚠';
  font-size: 18px;
  flex-shrink: 0;
}

/* ============================================================
   Success Message (inline success feedback)
   ============================================================ */
#success-msg {
  background-color: #E6F7E6;
  border: var(--border-width-sm) solid #00AA00;
  color: #006600;
  font-size: 14px;
  font-weight: bold;
  margin-top: 8px;
  padding: 12px;
  box-shadow: var(--shadow-hard-xs);
  display: flex;
  align-items: center;
  gap: 8px;
}

#success-msg::before {
  content: '✓';
  font-size: 18px;
  flex-shrink: 0;
}

/* ============================================================
   Filter Section
   ============================================================ */
#filter-section {
  display: flex;
  gap: 12px;
  padding: 20px;
  background: var(--color-surface);
  border-bottom: var(--border-width) solid var(--color-border);
}

.filter-btn {
  padding: 10px 20px;
  font-size: 14px;
  font-weight: bold;
  background-color: var(--color-disabled);
  color: var(--color-text);
  border: var(--border-width-sm) solid var(--color-border);
  box-shadow: var(--shadow-hard-sm);
  cursor: pointer;
  text-transform: uppercase;
  transition: all var(--transition);
}

.filter-btn:hover {
  background-color: var(--color-surface);
  transform: translate(1px, 1px);
  box-shadow: 2px 2px 0px var(--color-border);
}

.filter-btn:active {
  transform: translate(2px, 2px);
  box-shadow: 1px 1px 0px var(--color-border);
}

.filter-btn:focus-visible {
  outline: none;
  transform: translate(1px, 1px);
  box-shadow: 2px 2px 0px var(--color-border);
}

/* Active filter state — bright yellow background */
.filter-btn.active {
  background-color: var(--color-accent-yellow);
  border: var(--border-width-sm) solid var(--color-border);
  color: var(--color-text);
  font-weight: bold;
  box-shadow: var(--shadow-hard-sm);
}

.filter-btn.active:hover {
  transform: translate(1px, 1px);
  box-shadow: 2px 2px 0px var(--color-border);
}

/* ============================================================
   Todo List
   ============================================================ */
#todo-list {
  list-style: none;
  min-height: 40px;
  background: var(--color-surface);
}

.todo-item {
  align-items: center;
  border: var(--border-width-sm) solid var(--color-border);
  border-bottom: none;
  display: flex;
  gap: 12px;
  padding: 16px;
  background: var(--color-surface);
  box-shadow: var(--shadow-hard-sm);
  transition: all var(--transition);
}

.todo-item:last-child {
  border-bottom: var(--border-width-sm) solid var(--color-border);
}

.todo-item:hover {
  transform: translate(1px, 1px);
  box-shadow: 2px 2px 0px var(--color-border);
}

/* Checkbox */
.todo-checkbox {
  accent-color: var(--color-accent-yellow);
  cursor: pointer;
  flex-shrink: 0;
  height: 20px;
  width: 20px;
  border: var(--border-width-sm) solid var(--color-border);
}

/* Task text */
.todo-text {
  color: var(--color-text);
  flex: 1;
  font-size: 16px;
  font-weight: 400;
  line-height: 1.5;
  overflow-wrap: break-word;
  word-break: break-word;
}

/* Completed item — strikethrough on text */
.todo-item.completed .todo-text {
  color: var(--color-completed-text);
  text-decoration: line-through;
}

/* Delete button — hot pink accent */
.delete-btn {
  background-color: var(--color-accent-pink);
  color: #FFFFFF;
  border: var(--border-width-sm) solid var(--color-border);
  box-shadow: var(--shadow-hard-xs);
  cursor: pointer;
  flex-shrink: 0;
  font-size: 14px;
  font-weight: bold;
  letter-spacing: 0.5px;
  line-height: 1;
  min-height: 44px;
  min-width: 44px;
  padding: 6px 12px;
  text-transform: uppercase;
  transition: all var(--transition);
}

.delete-btn:hover {
  transform: translate(1px, 1px);
  box-shadow: 1px 1px 0px var(--color-border);
}

.delete-btn:active {
  transform: translate(2px, 2px);
  box-shadow: 0px 0px 0px var(--color-border);
}

.delete-btn:focus-visible {
  outline: none;
  transform: translate(1px, 1px);
  box-shadow: 1px 1px 0px var(--color-border);
}

/* Empty state message */
.empty-state {
  color: var(--color-text-muted);
  font-style: italic;
  padding: 24px 0;
  text-align: center;
}

/* ============================================================
   Summary Footer
   ============================================================ */
#summary-footer {
  align-items: center;
  border-top: var(--border-width) solid var(--color-border);
  display: flex;
  justify-content: space-between;
  padding: 16px 20px;
  background: var(--color-surface);
}

#summary-count {
  color: var(--color-text);
  font-size: 16px;
  font-weight: bold;
  line-height: 1.5;
}

#clear-completed-btn {
  padding: 10px 20px;
  font-size: 14px;
  font-weight: bold;
  background-color: var(--color-accent-pink);
  color: #FFFFFF;
  border: var(--border-width-sm) solid var(--color-border);
  box-shadow: var(--shadow-hard-sm);
  cursor: pointer;
  text-transform: uppercase;
  transition: all var(--transition);
}

#clear-completed-btn:hover {
  transform: translate(1px, 1px);
  box-shadow: 2px 2px 0px var(--color-border);
}

#clear-completed-btn:active {
  transform: translate(2px, 2px);
  box-shadow: 1px 1px 0px var(--color-border);
}

#clear-completed-btn:focus-visible {
  outline: none;
  transform: translate(1px, 1px);
  box-shadow: 2px 2px 0px var(--color-border);
}

/* ============================================================
   Storage Error Banner
   ============================================================ */
.storage-error-banner {
  align-items: center;
  background-color: var(--color-accent-pink);
  border: var(--border-width) solid var(--color-border);
  color: #FFFFFF;
  display: flex;
  font-size: 14px;
  font-weight: bold;
  gap: 12px;
  justify-content: space-between;
  margin: 0 auto 16px;
  max-width: 600px;
  padding: 16px;
  box-shadow: var(--shadow-hard);
}

#storage-error-close {
  background-color: transparent;
  border: none;
  color: #FFFFFF;
  cursor: pointer;
  flex-shrink: 0;
  font-size: 1rem;
  line-height: 1;
  padding: 2px 6px;
  transition: opacity var(--transition), transform var(--transition);
}

#storage-error-close:hover {
  opacity: 0.8;
  transform: translate(1px, 1px);
}

#storage-error-close:active {
  transform: translate(2px, 2px);
}

#storage-error-close:focus-visible {
  outline: none;
  transform: translate(1px, 1px);
}

/* ============================================================
   Responsive Design
   ============================================================ */

/* Mobile Viewport: ≤ 600px */
@media (max-width: 600px) {
  /* Body and Layout */
  body {
    padding: 12px 8px 32px;
    font-size: 14px;
  }

  #app {
    padding: 0;
    max-width: 100%;
  }

  /* Header */
  header {
    padding: 16px 12px;
    border-bottom: 3px solid var(--color-border);
  }

  header h1 {
    font-size: 24px;
    letter-spacing: 1px;
    line-height: 1.2;
  }

  /* Input Section */
  #input-section {
    padding: 12px;
  }

  .input-row {
    flex-direction: column;
    gap: 8px;
  }

  #task-input {
    padding: 10px;
    font-size: 14px;
    border: 3px solid var(--color-border);
    box-shadow: 2px 2px 0px var(--color-border);
    min-height: 44px;
  }

  #task-input:focus {
    box-shadow: 1px 1px 0px var(--color-border);
  }

  #add-btn {
    width: 100%;
    padding: 10px 16px;
    font-size: 14px;
    border: 3px solid var(--color-border);
    box-shadow: 2px 2px 0px var(--color-border);
    min-height: 44px;
  }

  #add-btn:hover {
    box-shadow: 1px 1px 0px var(--color-border);
  }

  #add-btn:active {
    box-shadow: 0px 0px 0px var(--color-border);
  }

  /* Error Message */
  #error-msg {
    font-size: 12px;
    border: 2px solid var(--color-accent-pink);
    padding: 6px;
    margin-top: 6px;
  }

  /* Filter Section */
  #filter-section {
    gap: 6px;
    padding: 12px;
    border-bottom: 3px solid var(--color-border);
    justify-content: center;
    flex-wrap: wrap;
  }

  .filter-btn {
    font-size: 11px;
    padding: 8px 12px;
    border: 2px solid var(--color-border);
    box-shadow: 2px 2px 0px var(--color-border);
    min-height: 40px;
    flex: 1;
    min-width: 70px;
  }

  .filter-btn:hover {
    box-shadow: 1px 1px 0px var(--color-border);
  }

  .filter-btn.active {
    box-shadow: 2px 2px 0px var(--color-border);
  }

  /* Todo List */
  #todo-list {
    min-height: 40px;
  }

  .todo-item {
    gap: 8px;
    padding: 12px;
    border: 2px solid var(--color-border);
    box-shadow: 2px 2px 0px var(--color-border);
  }

  .todo-item:hover {
    box-shadow: 1px 1px 0px var(--color-border);
  }

  .todo-checkbox {
    width: 18px;
    height: 18px;
    border: 2px solid var(--color-border);
    min-flex: 0;
  }

  .todo-text {
    font-size: 13px;
    line-height: 1.4;
  }

  .delete-btn {
    padding: 6px 10px;
    font-size: 12px;
    border: 2px solid var(--color-border);
    box-shadow: 1px 1px 0px var(--color-border);
    min-height: 40px;
    min-width: 40px;
  }

  .delete-btn:hover {
    box-shadow: 1px 1px 0px var(--color-border);
  }

  .delete-btn:active {
    box-shadow: 0px 0px 0px var(--color-border);
  }

  /* Summary Footer */
  #summary-footer {
    padding: 12px;
    border-top: 3px solid var(--color-border);
    flex-direction: column;
    gap: 8px;
    align-items: flex-start;
  }

  #summary-count {
    font-size: 13px;
  }

  #clear-completed-btn {
    width: 100%;
    padding: 10px 16px;
    font-size: 12px;
    border: 2px solid var(--color-border);
    box-shadow: 2px 2px 0px var(--color-border);
    min-height: 40px;
  }

  #clear-completed-btn:hover {
    box-shadow: 1px 1px 0px var(--color-border);
  }

  /* Storage Error Banner */
  .storage-error-banner {
    margin: 0 8px 12px;
    padding: 12px;
    font-size: 12px;
    border: 3px solid var(--color-border);
    box-shadow: 2px 2px 0px var(--color-border);
  }

  #storage-error-close {
    font-size: 0.9rem;
  }

  /* Empty State */
  .empty-state {
    padding: 16px;
    font-size: 12px;
  }
}

/* Tablet Viewport: 601px - 1024px */
@media (min-width: 601px) and (max-width: 1024px) {
  /* Body and Layout */
  body {
    padding: 20px 16px 40px;
    font-size: 15px;
  }

  #app {
    max-width: 90%;
  }

  /* Header */
  header {
    padding: 18px 16px;
    border-bottom: 4px solid var(--color-border);
  }

  header h1 {
    font-size: 30px;
    letter-spacing: 1.5px;
    line-height: 1.2;
  }

  /* Input Section */
  #input-section {
    padding: 16px;
  }

  .input-row {
    gap: 10px;
  }

  #task-input {
    padding: 11px;
    font-size: 15px;
    border: 3px solid var(--color-border);
    box-shadow: 3px 3px 0px var(--color-border);
    min-height: 44px;
  }

  #task-input:focus {
    box-shadow: 2px 2px 0px var(--color-border);
  }

  #add-btn {
    padding: 11px 22px;
    font-size: 15px;
    border: 3px solid var(--color-border);
    box-shadow: 3px 3px 0px var(--color-border);
    min-height: 44px;
  }

  #add-btn:hover {
    box-shadow: 2px 2px 0px var(--color-border);
  }

  /* Error Message */
  #error-msg {
    font-size: 13px;
    border: 3px solid var(--color-accent-pink);
    padding: 8px;
    margin-top: 8px;
  }

  /* Filter Section */
  #filter-section {
    gap: 10px;
    padding: 16px;
    border-bottom: 4px solid var(--color-border);
    justify-content: center;
  }

  .filter-btn {
    font-size: 13px;
    padding: 10px 18px;
    border: 3px solid var(--color-border);
    box-shadow: 3px 3px 0px var(--color-border);
    min-height: 44px;
  }

  .filter-btn:hover {
    box-shadow: 2px 2px 0px var(--color-border);
  }

  .filter-btn.active {
    box-shadow: 3px 3px 0px var(--color-border);
  }

  /* Todo List */
  .todo-item {
    gap: 12px;
    padding: 14px;
    border: 3px solid var(--color-border);
    box-shadow: 3px 3px 0px var(--color-border);
  }

  .todo-item:hover {
    box-shadow: 2px 2px 0px var(--color-border);
  }

  .todo-checkbox {
    width: 20px;
    height: 20px;
    border: 3px solid var(--color-border);
  }

  .todo-text {
    font-size: 15px;
    line-height: 1.5;
  }

  .delete-btn {
    padding: 8px 14px;
    font-size: 13px;
    border: 3px solid var(--color-border);
    box-shadow: 2px 2px 0px var(--color-border);
    min-height: 44px;
    min-width: 44px;
  }

  .delete-btn:hover {
    box-shadow: 1px 1px 0px var(--color-border);
  }

  /* Summary Footer */
  #summary-footer {
    padding: 14px 16px;
    border-top: 4px solid var(--color-border);
  }

  #summary-count {
    font-size: 15px;
  }

  #clear-completed-btn {
    padding: 10px 18px;
    font-size: 13px;
    border: 3px solid var(--color-border);
    box-shadow: 3px 3px 0px var(--color-border);
    min-height: 44px;
  }

  #clear-completed-btn:hover {
    box-shadow: 2px 2px 0px var(--color-border);
  }

  /* Storage Error Banner */
  .storage-error-banner {
    margin: 0 auto 16px;
    padding: 14px;
    font-size: 13px;
    border: 4px solid var(--color-border);
    box-shadow: 3px 3px 0px var(--color-border);
  }

  /* Empty State */
  .empty-state {
    padding: 20px;
    font-size: 14px;
  }
}

/* Desktop Viewport: > 1024px */
@media (min-width: 1025px) {
  /* Body and Layout */
  body {
    padding: 24px 16px 48px;
    font-size: 16px;
  }

  #app {
    max-width: 600px;
  }

  /* Header */
  header {
    padding: 20px;
    border-bottom: 4px solid var(--color-border);
  }

  header h1 {
    font-size: 36px;
    letter-spacing: 2px;
    line-height: 1.2;
  }

  /* Input Section */
  #input-section {
    padding: 20px;
  }

  .input-row {
    gap: 8px;
  }

  #task-input {
    padding: 12px;
    font-size: 16px;
    border: 4px solid var(--color-border);
    box-shadow: 4px 4px 0px var(--color-border);
    min-height: 44px;
  }

  #task-input:focus {
    box-shadow: 2px 2px 0px var(--color-border);
  }

  #add-btn {
    padding: 12px 24px;
    font-size: 16px;
    border: 4px solid var(--color-border);
    box-shadow: 4px 4px 0px var(--color-border);
    min-height: 44px;
  }

  #add-btn:hover {
    box-shadow: 2px 2px 0px var(--color-border);
  }

  /* Error Message */
  #error-msg {
    font-size: 14px;
    border: 3px solid var(--color-accent-pink);
    padding: 8px;
    margin-top: 8px;
  }

  /* Filter Section */
  #filter-section {
    gap: 12px;
    padding: 20px;
    border-bottom: 4px solid var(--color-border);
    justify-content: flex-start;
  }

  .filter-btn {
    font-size: 14px;
    padding: 10px 20px;
    border: 3px solid var(--color-border);
    box-shadow: 3px 3px 0px var(--color-border);
    min-height: 44px;
  }

  .filter-btn:hover {
    box-shadow: 2px 2px 0px var(--color-border);
  }

  .filter-btn.active {
    box-shadow: 4px 4px 0px var(--color-border);
  }

  /* Todo List */
  .todo-item {
    gap: 12px;
    padding: 16px;
    border: 3px solid var(--color-border);
    box-shadow: 3px 3px 0px var(--color-border);
  }

  .todo-item:hover {
    box-shadow: 2px 2px 0px var(--color-border);
  }

  .todo-checkbox {
    width: 20px;
    height: 20px;
    border: 3px solid var(--color-border);
  }

  .todo-text {
    font-size: 16px;
    line-height: 1.5;
  }

  .delete-btn {
    padding: 6px 12px;
    font-size: 14px;
    border: 3px solid var(--color-border);
    box-shadow: 2px 2px 0px var(--color-border);
    min-height: 44px;
    min-width: 44px;
  }

  .delete-btn:hover {
    box-shadow: 1px 1px 0px var(--color-border);
  }

  /* Summary Footer */
  #summary-footer {
    padding: 16px 20px;
    border-top: 4px solid var(--color-border);
  }

  #summary-count {
    font-size: 16px;
  }

  #clear-completed-btn {
    padding: 10px 20px;
    font-size: 14px;
    border: 3px solid var(--color-border);
    box-shadow: 3px 3px 0px var(--color-border);
    min-height: 44px;
  }

  #clear-completed-btn:hover {
    box-shadow: 2px 2px 0px var(--color-border);
  }

  /* Storage Error Banner */
  .storage-error-banner {
    margin: 0 auto 16px;
    padding: 16px;
    font-size: 14px;
    border: 4px solid var(--color-border);
    box-shadow: 4px 4px 0px var(--color-border);
  }

  /* Empty State */
  .empty-state {
    padding: 24px;
    font-size: 16px;
  }
}