:root {
  --bg: #0f1115;
  --surface: #1a1d24;
  --surface-2: #232731;
  --border: #2d313d;
  --text: #e8eaf0;
  --text-dim: #9aa0b0;
  --accent: #6c8cff;
  --accent-hover: #5a78f0;
  --danger: #ff6b6b;
  --success: #4ade80;
  --radius: 12px;
  --space: 16px;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  display: flex;
  justify-content: center;
  padding: 24px 16px;
  line-height: 1.5;
}

.app {
  width: 100%;
  max-width: 560px;
}

/* Header */
.app__header {
  text-align: center;
  margin-bottom: 28px;
}

.app__title {
  font-size: 2rem;
  font-weight: 800;
  letter-spacing: -0.5px;
}

.app__subtitle {
  color: var(--text-dim);
  font-size: 0.95rem;
  margin-top: 4px;
}

/* Form */
.todo-form {
  display: flex;
  gap: 10px;
  margin-bottom: 16px;
}

.todo-form__input {
  flex: 1;
  padding: 14px 16px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text);
  font-size: 1rem;
  transition: border-color 0.2s, box-shadow 0.2s;
}

.todo-form__input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(108, 140, 255, 0.2);
}

.todo-form__input::placeholder {
  color: var(--text-dim);
}

.todo-form__btn {
  padding: 14px 22px;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: var(--radius);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s;
}

.todo-form__btn:hover {
  background: var(--accent-hover);
}

/* Filters */
.filters {
  display: flex;
  gap: 6px;
  margin-bottom: 16px;
  background: var(--surface);
  padding: 4px;
  border-radius: var(--radius);
  width: fit-content;
}

.filters__btn {
  padding: 8px 18px;
  background: transparent;
  border: none;
  border-radius: 8px;
  color: var(--text-dim);
  font-size: 0.9rem;
  cursor: pointer;
  transition: all 0.2s;
}

.filters__btn:hover {
  color: var(--text);
}

.filters__btn.is-active {
  background: var(--accent);
  color: #fff;
}

/* Todo list */
.todo-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.todo-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px 16px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  transition: border-color 0.2s, opacity 0.2s;
}

.todo-item:hover {
  border-color: var(--accent);
}

/* Checkbox */
.todo-item__check {
  position: relative;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 24px;
  height: 24px;
  flex-shrink: 0;
}

.todo-item__checkbox {
  position: absolute;
  opacity: 0;
  width: 100%;
  height: 100%;
  cursor: pointer;
  margin: 0;
}

.todo-item__box {
  width: 24px;
  height: 24px;
  border: 2px solid var(--border);
  border-radius: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s;
}

.todo-item__checkbox:checked + .todo-item__box {
  background: var(--success);
  border-color: var(--success);
}

.todo-item__checkbox:checked + .todo-item__box::after {
  content: "✓";
  color: #fff;
  font-size: 14px;
  font-weight: bold;
}

.todo-item__checkbox:focus-visible + .todo-item__box {
  box-shadow: 0 0 0 3px rgba(108, 140, 255, 0.4);
}

/* Text */
.todo-item__text {
  flex: 1;
  font-size: 1rem;
  cursor: pointer;
  word-break: break-word;
  transition: color 0.2s;
}

.todo-item--done .todo-item__text {
  color: var(--text-dim);
  text-decoration: line-through;
}

.todo-item__text[contenteditable="true"] {
  outline: 2px solid var(--border);
  outline-offset: 2px;
  border-radius: 4px;
  padding: 2px 4px;
}

/* Delete */
.todo-item__delete {
  background: none;
  border: none;
  color: var(--text-dim);
  font-size: 1rem;
  cursor: pointer;
  padding: 4px 8px;
  border-radius: 6px;
  transition: all 0.2s;
  flex-shrink: 0;
}

.todo-item__delete:hover {
  background: rgba(255, 107, 107, 0.15);
  color: var(--danger);
}

/* Empty state */
.empty {
  text-align: center;
  color: var(--text-dim);
  padding: 48px 16px;
  font-size: 0.95rem;
}

/* Footer */
.app__footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 20px;
  padding-top: 16px;
  border-top: 1px solid var(--border);
  font-size: 0.85rem;
  color: var(--text-dim);
}

.clear-btn {
  background: none;
  border: none;
  color: var(--text-dim);
  font-size: 0.85rem;
  cursor: pointer;
  transition: color 0.2s;
}

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

.clear-btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

/* Responsive */
@media (max-width: 480px) {
  .app__title { font-size: 1.6rem; }
  .todo-form { flex-direction: column; }
  .todo-form__btn { width: 100%; }
  .filters { width: 100%; }
  .filters__btn { flex: 1; }
  .app__footer { flex-direction: column; gap: 10px; }
}

@media (prefers-reduced-motion: reduce) {
  * { transition: none !important; }
}