* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: system-ui, -apple-system, "PingFang SC", "Microsoft YaHei", "Noto Sans CJK SC", sans-serif;
  background: #f4f5f7;
  color: #1f2328;
}

.app {
  max-width: 560px;
  margin: 40px auto;
  padding: 24px;
  background: #fff;
  border-radius: 8px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.12);
}

h1 {
  margin: 0 0 16px;
  font-size: 28px;
}

.todo-form {
  display: flex;
  gap: 8px;
  margin-bottom: 16px;
}

.todo-input {
  flex: 1;
  padding: 8px 10px;
  font-size: 16px;
  border: 1px solid #c9ced6;
  border-radius: 4px;
}

button {
  font: inherit;
  cursor: pointer;
}

.todo-add {
  padding: 8px 16px;
  border: none;
  border-radius: 4px;
  background: #2563eb;
  color: #fff;
}

.filters {
  display: flex;
  gap: 8px;
  margin-bottom: 12px;
}

.filter {
  padding: 4px 12px;
  border: 1px solid #c9ced6;
  border-radius: 4px;
  background: #fff;
  color: #1f2328;
}

.filter.is-selected {
  font-weight: 700;
  background: #dbe7ff;
  border-color: #2563eb;
}

.todo-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.todo-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 4px;
  border-bottom: 1px solid #eceef1;
}

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

.todo-item.is-completed .todo-text {
  text-decoration: line-through;
  color: #8b929b;
}

.todo-delete {
  padding: 2px 10px;
  border: 1px solid #e5484d;
  border-radius: 4px;
  background: #fff;
  color: #e5484d;
}

.empty-state {
  margin: 16px 0 0;
  color: #8b929b;
  text-align: center;
}

.todo-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-top: 16px;
  padding-top: 12px;
  border-top: 1px solid #c9ced6;
}

.remaining-count {
  color: #4b525b;
}

.clear-completed {
  padding: 4px 12px;
  border: 1px solid #2563eb;
  border-radius: 4px;
  background: #fff;
  color: #2563eb;
}

.clear-completed:disabled {
  opacity: 0.5;
  border-color: #c9ced6;
  color: #8b929b;
  cursor: not-allowed;
}