* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
body {
  width: 100%;
  height: 100vh;
  font-family: sans-serif;
  background-color: #fbf7ee;
  font-size: 16px;
  display: flex;
  justify-content: center;
  align-items: center;
}
.container {
  width: 90%;
  max-width: 600px;
  height: 500px;
  background-color: #fff;
  border: 10px solid #f77f00;
  border-radius: 10px;
  box-shadow: 2px 2px 4px #666;
  padding: 20px;
  text-align: center;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
}
h1 {
  font-size: 2rem;
  margin-bottom: 40px;
}
h2 {
  font-size: 2rem;
  margin-bottom: 40px;
}
.btns {
  display: flex;
  justify-content: center;
  gap: 12px;
}
button {
  font-size: 1.4rem;
  padding: 10px 20px;
  border-radius: 5px;
  border: none;
  cursor: pointer;
  margin: 5px;
}
.startBtn,
.resetBtn {
  background-color: #0d6efd;
  color: #fff;
}
.okBtn {
  background-color: #198754;
  color: #fff;
}
.changeBtn {
  background-color: #dc3545;
  color: #fff;
}
.startBtn.hide {
  display: none;
}
.btns.hide {
  display: none;
}
.resetBtn.hide {
  display: none;
}