:root {
  --bg: #f5f7fb;
  --card: #ffffff;
  --text: #1f2937;
  --muted: #6b7280;
  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --danger: #ef4444;
  --border: #e5e7eb;
  --done: #9ca3af;
  --shadow: 0 10px 25px rgba(15, 23, 42, 0.08);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: linear-gradient(180deg, #eef2ff 0%, var(--bg) 100%);
  color: var(--text);
  display: flex;
  justify-content: center;
  padding: 40px 16px;
}

.app {
  width: 100%;
  max-width: 560px;
  background: var(--card);
  border-radius: 16px;
  box-shadow: var(--shadow);
  padding: 28px;
}

.app-header h1 {
  margin: 0;
  font-size: 28px;
  letter-spacing: -0.5px;
}

.subtitle {
  margin: 6px 0 22px;
  color: var(--muted);
  font-size: 14px;
}

.todo-form {
  display: flex;
  gap: 10px;
}

.todo-input {
  flex: 1;
  padding: 12px 14px;
  border: 1px solid var(--border);
  border-radius: 10px;
  font-size: 15px;
  outline: none;
  transition: border-color 0.2s, box-shadow 0.2s;
}

.todo-input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.15);
}

.add-btn {
  padding: 12px 18px;
  border: none;
  border-radius: 10px;
  background: var(--primary);
  color: #fff;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s;
}

.add-btn:hover {
  background: var(--primary-hover);
}

.todo-stats {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin: 18px 0 10px;
  color: var(--muted);
  font-size: 13px;
}

.clear-btn {
  background: transparent;
  border: none;
  color: var(--muted);
  cursor: pointer;
  font-size: 13px;
}

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

.todo-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.todo-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 14px;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: #fff;
  transition: background 0.2s, transform 0.1s;
}

.todo-item:hover {
  background: #fafafa;
}

.todo-item input[type="checkbox"] {
  width: 18px;
  height: 18px;
  accent-color: var(--primary);
  cursor: pointer;
  flex-shrink: 0;
}

.todo-text {
  flex: 1;
  font-size: 15px;
  word-break: break-word;
}

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

.delete-btn {
  border: none;
  background: transparent;
  color: var(--muted);
  font-size: 18px;
  line-height: 1;
  cursor: pointer;
  padding: 4px 8px;
  border-radius: 6px;
  transition: background 0.2s, color 0.2s;
}

.delete-btn:hover {
  background: #fee2e2;
  color: var(--danger);
}

.empty-state {
  margin: 24px 0 0;
  text-align: center;
  color: var(--muted);
  font-size: 14px;
}

.empty-state.hidden {
  display: none;
}