HTMLify

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  padding: 0;
  font-family: Arial, Helvetica, sans-serif;
}

.header {
  position: relative;
  top: -20px;
  width: 100%;
  background-color: #011627;
  color: #fdfffc;
}

.header h2 {
  padding: 0.5em;
}

div.n-queen {
  position: absolute;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 70%;
  max-width: 450px;
  /* border: 1px solid red; */
}

.inputbox {
  position: relative;
  top: 1.5em;
  bottom: 2em;
}

.numberbox {
  width: 100%;
  font-size: 14px;
  padding: 4px;
  border: none;
  border-bottom: 2px solid #2ec4b6;
  outline: none;
  background: transparent;
}

.inputbox label {
  position: absolute;
  top: 4px;
  left: 0px;
  color: #2ec4b6;
  font-size: 14px;
  pointer-events: none;
  transition: 0.3s;
}

.inputbox input:focus ~ label,
.inputbox input:disabled ~ label,
.inputbox input:valid ~ label {
  top: -9px;
  font-size: 12px;
  font-weight: 400;
}

.slider-container {
  position: absolute;
  left: 5%;
  width: 90%;
  /* text-align: center; */
  margin: 0 auto;
  top: 4em;
  /* border: 2px solid red; */
}

.slider {
  -webkit-appearance: none;
  width: 100%;
  margin: 0 auto;
  height: 7px;
  border-radius: 7px;
  background: linear-gradient(90deg, #e8eddf 60%, #e8eddf 60%);
  outline: none;
}

.slider::after {
  content: "SLOW";
  position: absolute;
  top: -10px;
  font-size: 14px;
  font-weight: 500;
  color: #fa7921;
}

.slider::before {
  content: "FAST";
  position: absolute;
  top: -10px;
  right: 0px;
  font-size: 14px;
  font-weight: 500;
  color: #fa7921;
}

/* Google chrome */
.slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 20px;
  height: 20px;
  position: relative;
  top: -2px;
  cursor: pointer;
  background-color: #fa7921;
  border-radius: 50%;
  z-index: 2;
}

.slider::-webkit-slider-runnable-track {
  -webkit-appearance: none;
  height: 15px;
  width: 15px;
  z-index: 1;
  color: #ffba08;
}

/* Mozilla firefox */
.slider::-moz-range-thumb {
  width: 20px;
  height: 20px;
  background-color: #fa7921;
  cursor: pointer;
  position: relative;
  top: -2px;
  border-radius: 50%;
  z-index: 2;
}

.slider::-webkit-slider-thumb:hover {
  box-shadow: 0 0 0 2px white, 0 0 0 4px #fa7921;
}

#progress-bar {
  width: 60%;
  height: 7px;
  background: #ffd200;
  border-radius: 7px;
  position: absolute;
  top: 7px;
}

.play-button {
  position: relative;
  top: 80px;
  left: 35%;
  border: none;
  outline: none;
  color: #fdfffc;
  width: 80px;
  height: 35px;
  background-color: #f72585;
  border-radius: 10px;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.3s ease-in-out;
  /* z-index: 1; */
}

.play-button:hover {
  opacity: 0.8;
  transform: scale(1.05);
}

.queen-arrangement {
  position: relative;
  top: 140px;
  text-align: center;
  font-size: 18px;
  font-weight: 500;
  color: #247ba0;
}

#n-queen-board {
  position: relative;
  display: flex;
  width: 80%;
  top: 150px;
  margin: 0 auto;
  flex-wrap: wrap;
  justify-content: center;
}

#n-queen-board div {
  position: relative;
  display: flex;
  justify-content: center;
  flex-direction: column;
  margin: 0 10px;
  box-shadow: 0 4px 8px 0 rgb(0, 0, 0, 0.2);
  border-radius: 3px;
  bottom: 10px;
}

table {
  position: relative;
  border-collapse: collapse;
  margin: -10px 10px;
  padding: 10px;
  margin-bottom: 10px;
  align-self: center;
}

td {
  width: 35px;
  height: 35px;
  text-align: center;
}

h4 {
  position: relative;
  top: -5px;
  padding: 8px;
  width: 95%;
  background-color: #0582ca;
  align-self: center;
  color: #fdfffc;
  text-align: center;
  border-radius: 4px 4px 0 0;
}