body {
  margin: 0;
  padding: 0;
  font-family: 'Roboto', sans-serif;
  background-color: #f0f4f8;
  color: #333;
  display: flex;
  flex-direction: column;
  align-items: center;
  min-height: 100vh;
}

header {
  text-align: center;
  margin-top: 20px;
}

#days-container {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(60px, 1fr));
  gap: 10px;
  max-width: 600px;
  width: 100%;
  margin: 20px 0;
  padding: 0 10px;
}

.day {
  width: 60px;
  height: 60px;
  background-color: #fff;
  border: 2px solid #ccc;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  border-radius: 4px;
  font-weight: bold;
  transition: background-color 0.3s, border-color 0.3s;
}

.day.completed {
  background-color: #9ae6b4;
  border-color: #68d391;
  color: #fff;
}

#reset {
  background-color: #e53e3e;
  color: #fff;
  border: none;
  padding: 10px 20px;
  font-size: 1rem;
  border-radius: 4px;
  cursor: pointer;
  margin-bottom: 20px;
  transition: background-color 0.3s;
}

#reset:hover {
  background-color: #c53030;
}