body {
  font-family: Arial, sans-serif;
  background: #f4f4f4;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

.container {
  background: white;
  padding: 20px;
  border-radius: 10px;
  width: 400px;
  box-shadow: 0 5px 15px rgba(0,0,0,0.1);
}

h1 {
  text-align: center;
}

.input-group {
  display: flex;
  gap: 10px;
}

input {
  flex: 1;
  padding: 10px;
}

button {
  padding: 10px;
  border: none;
  background: #007bff;
  color: white;
  border-radius: 5px;
}

li {
  background: #fafafa;
  margin: 10px 0;
  padding: 10px;
  display: flex;
  justify-content: space-between;
  border-radius: 5px;
}

.completada {
  text-decoration: line-through;
  color: gray;
}

.filtros {
  margin-top: 15px;
  display: flex;
  justify-content: center;
  gap: 10px;
}

.activo {
  background: #28a745;
}