/* ============================================================
   TODO — minimalist stylesheet
   Palette: neutral grays, single accent (#4f46e5 indigo-600)
   ============================================================ */

/* ── Reset & base ────────────────────────────────────────── */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  /* Colors */
  --color-bg:          #f9f9fb;
  --color-surface:     #ffffff;
  --color-border:      #e4e4e7;
  --color-text:        #18181b;
  --color-text-muted:  #71717a;
  --color-done:        #a1a1aa;
  --color-accent:      #4f46e5;
  --color-accent-hover:#4338ca;
  --color-danger:      #e11d48;
  --color-danger-hover:#be123c;

  /* Typography */
  --font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --font-size-base: 1rem;       /* 16px */
  --font-size-sm:   0.875rem;   /* 14px */
  --font-size-lg:   1.125rem;   /* 18px */
  --font-size-xl:   1.375rem;   /* 22px */
  --line-height:    1.5;

  /* Spacing */
  --space-1:  0.25rem;
  --space-2:  0.5rem;
  --space-3:  0.75rem;
  --space-4:  1rem;
  --space-6:  1.5rem;
  --space-8:  2rem;
  --space-12: 3rem;

  /* Shape */
  --radius-sm: 6px;
  --radius-md: 10px;

  /* Shadow */
  --shadow-card: 0 1px 4px 0 rgba(0, 0, 0, 0.07);
}

html {
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  line-height: var(--line-height);
  color: var(--color-text);
  background-color: var(--color-bg);
  -webkit-font-smoothing: antialiased;
}

/* ── Accessibility ───────────────────────────────────────── */
.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;
}

/* ── App shell ───────────────────────────────────────────── */
.app {
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: var(--space-8) var(--space-4) var(--space-12);
}

/* ── Header ──────────────────────────────────────────────── */
.app__header {
  width: 100%;
  max-width: 560px;
  margin-bottom: var(--space-6);
}

.app__title {
  font-size: var(--font-size-xl);
  font-weight: 600;
  letter-spacing: -0.01em;
  color: var(--color-text);
}

/* ── Main content ────────────────────────────────────────── */
.app__main {
  width: 100%;
  max-width: 560px;
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
}

/* ── Add-task form ───────────────────────────────────────── */
.add-form {
  display: flex;
  gap: var(--space-2);
}

.add-form__input {
  flex: 1;
  min-width: 0;
  padding: var(--space-3) var(--space-4);
  font-family: inherit;
  font-size: var(--font-size-base);
  color: var(--color-text);
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  outline: none;
  transition: border-color 0.15s, box-shadow 0.15s;
}

.add-form__input::placeholder {
  color: var(--color-text-muted);
}

.add-form__input:focus {
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.15);
}

.add-form__button {
  flex-shrink: 0;
  padding: var(--space-3) var(--space-6);
  font-family: inherit;
  font-size: var(--font-size-base);
  font-weight: 500;
  color: #ffffff;
  background-color: var(--color-accent);
  border: none;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: background-color 0.15s;
}

.add-form__button:hover {
  background-color: var(--color-accent-hover);
}

.add-form__button:focus-visible {
  outline: 3px solid var(--color-accent);
  outline-offset: 2px;
}

.add-form__button:active {
  transform: translateY(1px);
}

/* ── Task list ───────────────────────────────────────────── */
.task-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

/* ── Task item ───────────────────────────────────────────── */
.task-item {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-card);
  transition: border-color 0.15s;
}

.task-item:hover {
  border-color: #d4d4d8;
}

/* ── Task toggle (checkbox) ──────────────────────────────── */
.task-item__toggle {
  flex-shrink: 0;
  width: 20px;
  height: 20px;
  appearance: none;
  -webkit-appearance: none;
  border: 2px solid var(--color-border);
  border-radius: 50%;
  cursor: pointer;
  position: relative;
  transition: border-color 0.15s, background-color 0.15s;
  background-color: transparent;
}

.task-item__toggle:hover {
  border-color: var(--color-accent);
}

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

.task-item__toggle:checked {
  background-color: var(--color-accent);
  border-color: var(--color-accent);
}

/* Checkmark drawn with CSS */
.task-item__toggle:checked::after {
  content: '';
  display: block;
  position: absolute;
  top: 3px;
  left: 5px;
  width: 6px;
  height: 10px;
  border: 2px solid #ffffff;
  border-top: none;
  border-left: none;
  transform: rotate(45deg);
}

/* ── Task text ───────────────────────────────────────────── */
.task-item__text {
  flex: 1;
  min-width: 0;
  font-size: var(--font-size-base);
  color: var(--color-text);
  word-break: break-word;
  transition: color 0.15s, text-decoration-color 0.15s;
}

/* ── Done state ──────────────────────────────────────────── */
.task-item--done .task-item__text {
  text-decoration: line-through;
  text-decoration-color: var(--color-done);
  color: var(--color-done);
}

/* ── Delete button ───────────────────────────────────────── */
.task-item__delete {
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  padding: 0;
  background: none;
  border: none;
  border-radius: var(--radius-sm);
  cursor: pointer;
  color: var(--color-text-muted);
  font-size: var(--font-size-lg);
  line-height: 1;
  transition: color 0.15s, background-color 0.15s;
  opacity: 0;
}

.task-item:hover .task-item__delete,
.task-item:focus-within .task-item__delete {
  opacity: 1;
}

.task-item__delete:hover {
  color: var(--color-danger);
  background-color: rgba(225, 29, 72, 0.08);
}

.task-item__delete:focus-visible {
  opacity: 1;
  outline: 3px solid var(--color-danger);
  outline-offset: 2px;
  color: var(--color-danger);
}

/* ── Task counter ────────────────────────────────────────── */
.task-counter {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  margin-bottom: var(--space-2);
}

/* ── Empty state ─────────────────────────────────────────── */
.task-list__empty {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-12) var(--space-4);
  text-align: center;
}

.task-list__empty-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background-color: var(--color-border);
  color: var(--color-text-muted);
  font-size: var(--font-size-xl);
  line-height: 1;
  margin-bottom: var(--space-1);
}

.task-list__empty-text {
  font-size: var(--font-size-base);
  font-weight: 500;
  color: var(--color-text-muted);
}

.task-list__empty-hint {
  font-size: var(--font-size-sm);
  color: var(--color-done);
}

/* ── Touch devices: always show delete button ────────────── */
/* Hover is unavailable on touch screens; keep the button visible. */
@media (hover: none) {
  .task-item__delete {
    opacity: 1;
  }
}

/* ── Responsive (≤ 480 px) ───────────────────────────────── */
@media (max-width: 480px) {
  .app {
    padding: var(--space-6) var(--space-3) var(--space-8);
  }

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

  .add-form__button {
    width: 100%;
    text-align: center;
  }

  /* Tighter task card padding on narrow screens */
  .task-item {
    padding: var(--space-3);
  }
}