* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html,
body {
  height: 100%;
  width: 100%;
  font-family: Arial, sans-serif;
  background-color: #ffffff;
}

.container {
  display: flex;
  flex-direction: column;
  justify-content: flex-start;
  align-items: stretch;
  height: 100%;
  padding: 10px;
}

h1 {
  text-align: center;
  font-size: 24px;
  margin-bottom: 10px;
}

#series.flex {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  flex-grow: 1;
  gap: 8px;
}

#series.flex button {
  flex: 1 1 48%;
  height: 48%;
  font-size: 40px;
  font-weight: bold;
  border: none;
  border-radius: 8px;
  background-color: #007bff;
  color: white;
  cursor: pointer;
  padding: 20px;
}

#series button.active {
  background-color: #cc0000;
}

#timer {
  text-align: center;
  font-size: 32px;
  margin: 15px 0;
}

.controls {
  display: flex;
  justify-content: space-between;
  margin-bottom: 10px;
}

.controls button {
  flex: 1;
  margin: 0 5px;
  padding: 14px;
  font-size: 18px;
  background-color: #444;
  color: white;
  border: none;
  border-radius: 8px;
}

#status {
  text-align: center;
  font-size: 18px;
  padding: 10px;
}