/* ==========================================================================
   Task Manager — Day 7: Styling & Responsive Design
   Mobile-first. Breakpoints layered on top of a solid small-screen base.
   ========================================================================== */

:root {
  /* Color system */
  --color-primary: #4f46e5;
  --color-primary-dark: #4338ca;
  --color-primary-light: #eef2ff;
  --color-danger: #dc2626;
  --color-danger-dark: #b91c1c;
  --color-danger-light: #fef2f2;
  --color-bg: #f8f9fc;
  --color-surface: #ffffff;
  --color-text: #1f2330;
  --color-text-muted: #5a6270; /* darkened from #6b7280 for AA contrast compliance on white */
  --color-warning: #b45309;
  --color-warning-bg: #fffbeb;
  --color-warning-border: #fde68a;
  --color-border: #e5e7eb;
  --color-success: #16a34a;

  /* Spacing scale */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.5rem;
  --space-6: 2rem;
  --space-8: 3rem;

  /* Radius & shadow */
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --shadow-sm: 0 1px 2px rgba(16, 24, 40, 0.06);
  --shadow-md: 0 4px 12px rgba(16, 24, 40, 0.08);
  --shadow-focus: 0 0 0 3px rgba(79, 70, 229, 0.25);

  /* Motion */
  --transition-fast: 150ms ease;
  --transition-base: 220ms ease;
}

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

html {
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
    "Helvetica Neue", Arial, sans-serif;
  background-color: var(--color-bg);
  color: var(--color-text);
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

/* Respect reduced-motion preference */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
  }
}

/* Consistent, visible focus ring for keyboard users everywhere */
a:focus-visible,
button:focus-visible,
input:focus-visible {
  outline: none;
  box-shadow: var(--shadow-focus);
}

/* ---------- Header ---------- */
header {
  background: linear-gradient(135deg, var(--color-primary) 0%, #6366f1 100%);
  color: white;
  padding: var(--space-6) var(--space-4) var(--space-5);
  text-align: center;
}

header h1 {
  font-size: 1.5rem;
  font-weight: 700;
  letter-spacing: -0.01em;
}

header .tagline {
  margin-top: var(--space-1);
  font-size: 0.9rem;
  color: rgba(255, 255, 255, 0.85);
  font-weight: 400;
}

/* ---------- Main layout ---------- */
main {
  flex: 1;
  padding: var(--space-5) var(--space-4) var(--space-6);
  max-width: 600px;
  margin: 0 auto;
  width: 100%;
}

/* ---------- Form ---------- */
#task-form {
  display: flex;
  gap: var(--space-2);
  margin-top: calc(-1 * var(--space-8));
  margin-bottom: var(--space-4);
  background: var(--color-surface);
  padding: var(--space-3);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
}

#task-input {
  flex: 1;
  min-width: 0; /* prevents overflow on narrow screens */
  padding: 0.75rem 0.9rem;
  font-size: 1rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-bg);
  color: var(--color-text);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

#task-input::placeholder {
  color: #9ca3af;
}

#task-input:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: var(--shadow-focus);
  background: var(--color-surface);
}

#task-input.input-error {
  border-color: var(--color-danger);
  animation: shake 0.4s ease;
}

@keyframes shake {
  0%, 100% { transform: translateX(0); }
  25% { transform: translateX(-4px); }
  75% { transform: translateX(4px); }
}

#task-form button {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.75rem 1.1rem;
  font-size: 1rem;
  font-weight: 600;
  background-color: var(--color-primary);
  color: white;
  border: none;
  border-radius: var(--radius-sm);
  cursor: pointer;
  white-space: nowrap;
  transition: background-color var(--transition-fast), transform var(--transition-fast);
}

#task-form button:hover {
  background-color: var(--color-primary-dark);
}

#task-form button:active {
  transform: scale(0.97);
}

.btn-icon {
  font-size: 1.1rem;
  line-height: 1;
}

/* ---------- Inline alerts (validation error / storage warning) ---------- */
.form-error {
  display: none;
  color: var(--color-danger);
  background-color: var(--color-danger-light);
  border: 1px solid #fecaca;
  border-radius: var(--radius-sm);
  padding: var(--space-2) var(--space-3);
  font-size: 0.85rem;
  margin-bottom: var(--space-3);
}

.storage-warning {
  display: none;
  color: var(--color-warning);
  background-color: var(--color-warning-bg);
  border: 1px solid var(--color-warning-border);
  border-radius: var(--radius-sm);
  padding: var(--space-2) var(--space-3);
  font-size: 0.85rem;
  margin-bottom: var(--space-3);
}

.noscript-banner {
  background-color: #fef2f2;
  color: var(--color-danger-dark);
  text-align: center;
  padding: var(--space-3) var(--space-4);
  font-size: 0.9rem;
  border-bottom: 1px solid #fecaca;
}

/* ---------- Task summary ---------- */
.task-summary {
  display: none;
  font-size: 0.85rem;
  color: var(--color-text-muted);
  margin-bottom: var(--space-3);
  padding-left: var(--space-1);
}

/* ---------- Empty state ---------- */
#empty-message {
  display: none;
  text-align: center;
  color: var(--color-text-muted);
  font-style: normal;
  padding: var(--space-8) var(--space-4);
  background: var(--color-surface);
  border: 1px dashed var(--color-border);
  border-radius: var(--radius-md);
}

.empty-icon {
  display: block;
  font-size: 2rem;
  margin-bottom: var(--space-2);
}

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

.task-item {
  background-color: var(--color-surface);
  padding: var(--space-3) var(--space-3);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  display: flex;
  align-items: center;
  gap: var(--space-3);
  border: 1px solid transparent;
  transition: box-shadow var(--transition-fast), transform var(--transition-fast),
    opacity var(--transition-base), max-height var(--transition-base);
  animation: fadeInUp var(--transition-base);
}

.task-item:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--color-border);
}

.task-item.removing {
  opacity: 0;
  transform: translateX(12px);
}

@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(6px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.task-checkbox {
  width: 20px;
  height: 20px;
  min-width: 20px;
  cursor: pointer;
  flex-shrink: 0;
  accent-color: var(--color-primary);
}

.task-text {
  flex: 1;
  min-width: 0;
  word-break: break-word;
  font-size: 0.98rem;
  transition: color var(--transition-fast);
}

.task-item.completed {
  background-color: #fafafa;
}

.task-item.completed .task-text {
  text-decoration: line-through;
  color: #9ca3af;
}

.delete-btn {
  padding: 0.45rem 0.8rem;
  font-size: 0.82rem;
  font-weight: 600;
  background-color: transparent;
  color: var(--color-danger);
  border: 1px solid var(--color-danger-light);
  border-radius: var(--radius-sm);
  cursor: pointer;
  flex-shrink: 0;
  transition: background-color var(--transition-fast), color var(--transition-fast),
    border-color var(--transition-fast);
}

.delete-btn:hover {
  background-color: var(--color-danger);
  color: white;
  border-color: var(--color-danger);
}

.delete-btn:active {
  background-color: var(--color-danger-dark);
}

.delete-btn:disabled,
.task-checkbox:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

/* ---------- Footer ---------- */
footer {
  text-align: center;
  padding: var(--space-5) var(--space-4);
  font-size: 0.85rem;
  color: var(--color-text-muted);
  border-top: 1px solid var(--color-border);
  background: var(--color-surface);
}

.challenge-credit {
  margin-top: var(--space-1);
  font-size: 0.78rem;
  color: #9ca3af;
}

/* ==========================================================================
   Responsive breakpoints
   ========================================================================== */

/* Small phones (< 400px): tighten spacing further */
@media (max-width: 400px) {
  header {
    padding: var(--space-5) var(--space-3) var(--space-4);
  }

  header h1 {
    font-size: 1.3rem;
  }

  main {
    padding: var(--space-4) var(--space-3) var(--space-5);
  }

  #task-form {
    flex-direction: column;
    margin-top: calc(-1 * var(--space-6));
  }

  #task-form button {
    justify-content: center;
  }

  .btn-label {
    display: inline;
  }

  .task-item {
    padding: var(--space-3);
  }

  .delete-btn {
    padding: 0.4rem 0.6rem;
    font-size: 0.78rem;
  }
}

/* Tablets and up (>= 640px): a bit more breathing room */
@media (min-width: 640px) {
  main {
    padding: var(--space-6) var(--space-4) var(--space-8);
  }

  header {
    padding: var(--space-8) var(--space-4) var(--space-6);
  }

  header h1 {
    font-size: 1.75rem;
  }
}

/* Desktops (>= 900px): cap width, add a touch more polish */
@media (min-width: 900px) {
  main {
    max-width: 640px;
  }

  .task-item:hover {
    transform: translateY(-1px);
  }
}