style.css

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
body {
  font-family: Tahoma, Arial, Helvetica, serif;
}
.start {
  position: fixed;
  left: 0;
  height: 0;
  width: 100%;
  height: 100%;
  background-color: #35e69f;
  z-index: 4;
}
.start div {
  position: absolute;
  top: 44%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 420px;
}
.start div label {
  display: block;
  margin: 10px;
  text-align: left;
  user-select: none;
}
.start div input {
  display: block;
  padding: 2px 14px;
  line-height: 38px;
  border: none;
  border-bottom: 4px solid #888;
  outline: none;
  margin-bottom: 22px;
  width: 100%;
}
.start div button:hover {
  background-position: right;
}

.start div button {
  /* width: 100%; */
}
.container {
  width: 660px;
  height: 660px;
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  padding: 10px;
  margin: auto;
}
.container div {
  width: 32%;
  height: 32%;
  font-family: Tahoma, Arial;
  border: 1px solid #ccc;
  background-color: #98aef7;
  cursor: pointer;
  font-size: 168px;
  font-weight: bolder;
  text-align: center;
  color: #fff;
  user-select: none;
}
.players {
  width: 440px;
  margin: 20px auto;
  display: flex;
  justify-content: space-between;
  font-size: 22px;
}
button {
  background: linear-gradient(120deg, #999865, #1cbc9c, #7778db);
  background-size: 200%;
  border: 1px solid #fff;
  margin: 22px auto;
  height: 34px;
  outline: none;
  display: block;
  width: 400px;
  color: #fff;
  cursor: pointer;
  border-radius: 18px;
  transition: background-position 0.4s;
  user-select: none;
}