* {
  margin: 0;
  padding: 0;
  cursor: default;
}

body {
  background-color: #f1f1f1;
}

.container {
  background-color: #fff;
  width: 50%;
  height: 730px;
  margin: 5% 25%;
  border-radius: 0.5rem;
  box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2), 0 6px 20px 0 rgba(0, 0, 0, 0.19);
}

.head {
  background-color: #1897d4;
  padding: 2%;
  border-radius: 0.5rem 0.5rem 0 0;
}

.head .title {
  color: #fff;
  font-size: 30px;
  font-weight: 800;
  text-align: center;
}

.head .credit {
  text-align: right;
  margin: 2% 0 0 0;
  color: #fff;
  font-size: 20px;
  font-weight: 600;
}

.head .credit span:hover {
  text-decoration: underline;
  cursor: pointer;
}

#btn1,
#btn2,
#btn3,
#btn4 {
  padding: 2% 5%;
  color: #fff;
  font-size: 20px;
  font-weight: 800;
  border: 0;
  border-radius: 0.3rem;
  cursor: pointer;
  box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2), 0 6px 20px 0 rgba(0, 0, 0, 0.19);
}

#btn1 {
  background-color: #28a745;
  margin: 30% 40%;
}

#btn1:hover {
  background-color: #1e8b38;
}

#btn2 {
  display: none;
  background-color: #ffc107;
  margin: 5% 40% 0 40%;
  color: #000;
}

#btn2:hover {
  background-color: #eeb303;
}

#btn3 {
  display: none;
  background-color: #dc3545;
  margin: 5% 68%;
  color: #fff;
  font-size: 15px;
}

#btn3:hover {
  background-color: #c92434;
}

#btn4 {
  display: none;
  background-color: #ffc107;
  margin: 5% 40% 0 40%;
  color: #000;
}

#btn4:hover {
  background-color: #eeb303;
}

.timer-container {
  display: none;
  margin: 15% 40%;
  text-align: center;
  font-size: 100px;
  background-color: #fd7e14;
  color: #fff;
  font-weight: 800;
  border-radius: 50%;
  height: 16%;
  width: 26%;
  padding: 6% 0;
  box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2), 0 6px 20px 0 rgba(0, 0, 0, 0.19);
}

#today {
  text-align: center;
  margin: 5% 0;
  font-size: 30px;
  font-weight: 800;
  color: #343a40;
  display: none;
}

.stu-container {
  margin: 10% 25%;
  display: none;
}

.stu-container #stuId {
  text-align: center;
  font-size: 30px;
  font-weight: 800;
  color: #6610f2;
  width: 80%;
  margin: 0 10%;
  border-radius: 0.5rem;
  box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2), 0 6px 20px 0 rgba(0, 0, 0, 0.19);
}

.stu-container #stuName {
  text-align: center;
  font-size: 30px;
  font-weight: 800;
  color: #dc3545;
  width: 80%;
  margin: 10% 10%;
  border-radius: 0.5rem;
  box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2), 0 6px 20px 0 rgba(0, 0, 0, 0.19);
}

#topic-head {
  text-align: center;
  margin: 5% 0;
  font-size: 30px;
  font-weight: 800;
  color: #343a40;
  display: none;
}

#topic {
  text-align: center;
  font-size: 30px;
  font-weight: 800;
  color: #28a745;
  width: 80%;
  margin: 10% 10%;
  border-radius: 0.5rem;
  box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2), 0 6px 20px 0 rgba(0, 0, 0, 0.19);
}