:root {
  --bg: #f8fafc;
  --surface: #ffffff;
  --text: #0f172a;
  --text-muted: #64748b;
  --primary: #4f46e5;
  --primary-hover: #4338ca;
  --border: #e2e8f0;
  --danger: #ef4444;
  --shadow: 0 4px 6px -1px rgb(0 0 0 / 0.08), 0 2px 4px -2px rgb(0 0 0 / 0.06);
  --radius: 12px;
}

[data-theme="dark"] {
  --bg: #0f172a;
  --surface: #1e293b;
  --text: #f1f5f9;
  --text-muted: #94a3b8;
  --primary: #818cf8;
  --primary-hover: #a5b4fc;
  --border: #334155;
  --danger: #f87171;
  --shadow: 0 4px 6px -1px rgb(0 0 0 / 0.3), 0 2px 4px -2px rgb(0 0 0 / 0.2);
}

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

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100dvh;
  line-height: 1.5;
  transition: background 0.2s, color 0.2s;
}

.app {
  max-width: 480px;
  margin: 0 auto;
  padding: 1.5rem 1rem 3rem;
}

header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1.5rem;
}

h1 {
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.025em;
}

#theme-toggle {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 50%;
  width: 42px;
  height: 42px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
  box-shadow: var(--shadow);
  transition: transform 0.15s;
}

#theme-toggle:hover {
  transform: scale(1.05);
}

#theme-toggle .icon-moon {
  display: none;
}

[data-theme="dark"] #theme-toggle .icon-sun {
  display: none;
}

[data-theme="dark"] #theme-toggle .icon-moon {
  display: inline;
}

#todo-form {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 1.25rem;
}

#todo-input {
  flex: 1;
  padding: 0.85rem 1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--text);
  font-size: 1rem;
  outline: none;
  transition: border-color 0.15s, box-shadow 0.15s;
}

#todo-input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--primary) 25%, transparent);
}

#todo-form button[type="submit"] {
  width: 48px;
  height: 48px;
  border: none;
  border-radius: var(--radius);
  background: var(--primary);
  color: white;
  font-size: 1.5rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s, transform 0.1s;
  flex-shrink: 0;
}

#todo-form button[type="submit"]:hover {
  background: var(--primary-hover);
}

#todo-form button[type="submit"]:active {
  transform: scale(0.95);
}

#todo-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.todo-item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.9rem 1rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  animation: slideIn 0.25s ease;
}

@keyframes slideIn {
  from {
    opacity: 0;
    transform: translateY(-8px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

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

.todo-checkbox {
  width: 22px;
  height: 22px;
  accent-color: var(--primary);
  cursor: pointer;
  flex-shrink: 0;
}

.todo-text {
  flex: 1;
  word-break: break-word;
  font-size: 0.95rem;
}

.delete-btn {
  background: transparent;
  border: none;
  color: var(--text-muted);
  font-size: 1.25rem;
  cursor: pointer;
  padding: 0.25rem;
  line-height: 1;
  border-radius: 6px;
  transition: color 0.15s, background 0.15s;
}

.delete-btn:hover {
  color: var(--danger);
  background: color-mix(in srgb, var(--danger) 12%, transparent);
}

#footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 1.25rem;
  padding: 0.75rem 0.25rem;
  font-size: 0.875rem;
  color: var(--text-muted);
}

#footer.hidden {
  display: none;
}

#clear-completed {
  background: none;
  border: none;
  color: var(--primary);
  cursor: pointer;
  font-size: 0.875rem;
  font-weight: 500;
}

#clear-completed:hover {
  text-decoration: underline;
}

/* Install banner */
#install-banner {
  position: fixed;
  bottom: 1rem;
  left: 50%;
  transform: translateX(-50%);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.75rem 1rem;
  display: flex;
  align-items: center;
  gap: 0.75rem;
  box-shadow: var(--shadow);
  max-width: calc(100% - 2rem);
  z-index: 100;
  font-size: 0.9rem;
}

#install-banner.hidden {
  display: none;
}

#install-btn {
  background: var(--primary);
  color: white;
  border: none;
  padding: 0.4rem 0.85rem;
  border-radius: 8px;
  font-weight: 600;
  cursor: pointer;
  white-space: nowrap;
}

#dismiss-install {
  background: none;
  border: none;
  font-size: 1.25rem;
  color: var(--text-muted);
  cursor: pointer;
  line-height: 1;
}

.empty-state {
  text-align: center;
  padding: 2.5rem 1rem;
  color: var(--text-muted);
}

.empty-state p {
  margin-top: 0.5rem;
  font-size: 0.95rem;
}

/* Safe area for notched phones */
@supports (padding: max(0px)) {
  .app {
    padding-left: max(1rem, env(safe-area-inset-left));
    padding-right: max(1rem, env(safe-area-inset-right));
    padding-bottom: max(3rem, env(safe-area-inset-bottom));
  }
}