:root {
  --fg: #1a1a1a;
  --fg-muted: #6b7280;
  --bg: #fafafa;
  --card: #ffffff;
  --border: #e5e7eb;
  --accent: #2563eb;
  --danger: #dc2626;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif;
  background: var(--bg);
  color: var(--fg);
  line-height: 1.5;
}

main {
  max-width: 560px;
  margin: 3rem auto;
  padding: 0 1rem;
}

h1 {
  margin: 0 0 1.5rem;
  font-weight: 600;
}

input,
button {
  font-family: inherit;
  font-size: 1rem;
}

button {
  padding: 0.6rem 1rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--card);
  font-size: 0.95rem;
  cursor: pointer;
}

button:hover {
  border-color: var(--accent);
}

/* --- Auth view ---------------------------------------------------------- */

#auth-form {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1.5rem;
}

#auth-form label {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
  font-size: 0.9rem;
  color: var(--fg-muted);
}

#auth-form input {
  padding: 0.6rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: #fff;
  color: var(--fg);
}

#auth-form input:focus {
  outline: 2px solid var(--accent);
  outline-offset: -1px;
  border-color: transparent;
}

#auth-form button {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
  margin-top: 0.5rem;
}

.auth-toggle {
  margin-top: 1rem;
  font-size: 0.9rem;
  color: var(--fg-muted);
  text-align: center;
}

.auth-toggle a {
  color: var(--accent);
  text-decoration: none;
  margin-left: 0.25rem;
}

.auth-toggle a:hover {
  text-decoration: underline;
}

#auth-error {
  margin-top: 1rem;
  padding: 0.75rem;
  background: #fef2f2;
  color: var(--danger);
  border: 1px solid #fecaca;
  border-radius: 6px;
}

/* --- App view ----------------------------------------------------------- */

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

.app-header h1 {
  margin: 0;
}

.user-info {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  color: var(--fg-muted);
  font-size: 0.9rem;
}

#logout-btn {
  padding: 0.4rem 0.75rem;
  font-size: 0.85rem;
}

#new-todo-form {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 1rem;
}

#new-todo-form input {
  flex: 1;
  padding: 0.6rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--card);
}

#new-todo-form input:focus {
  outline: 2px solid var(--accent);
  outline-offset: -1px;
  border-color: transparent;
}

#new-todo-form button {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}

#filters {
  display: flex;
  gap: 0.25rem;
  margin-bottom: 1rem;
}

#filters button.active {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}

#todo-list {
  list-style: none;
  padding: 0;
  margin: 0;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
  overflow: hidden;
}

#todo-list:empty {
  display: none;
}

.todo {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--border);
}

.todo:last-child {
  border-bottom: none;
}

.todo input[type="checkbox"] {
  width: 18px;
  height: 18px;
  cursor: pointer;
}

.todo .title {
  flex: 1;
  word-break: break-word;
}

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

.todo .delete {
  border: none;
  background: transparent;
  color: var(--fg-muted);
  font-size: 1.25rem;
  line-height: 1;
  padding: 0.25rem 0.5rem;
}

.todo .delete:hover {
  color: var(--danger);
}

#empty {
  text-align: center;
  color: var(--fg-muted);
  margin-top: 2rem;
}

#error {
  margin-top: 1rem;
  padding: 0.75rem;
  background: #fef2f2;
  color: var(--danger);
  border: 1px solid #fecaca;
  border-radius: 6px;
}