style.css

*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: inherit;
  text-decoration: none;
}
html {
  box-sizing: border-box;
}

@font-face {
  font-family: "Roboto", sans-serif;
  src: url(./fonts/Roboto-Regular.ttf);
}

.main {
  height: 100vh;
  width: 100%;
  background-color: #ffd829;
  display: flex;
  justify-content: start;
  align-items: center;
  flex-direction: column;
}
.main__heading {
  text-align: center;
  margin-top: 4rem;
  font-family: "Roboto";
  font-size: 2rem;
  text-transform: uppercase;
  font-weight: 600;
}
@media only screen and (min-width: 400px) {
  .main__heading {
    font-size: 3rem;
  }
}
@media only screen and (min-width: 650px) {
  .main__heading {
    font-size: 4rem;
    margin-top: 5rem;
  }
}
@media only screen and (min-width: 900px) {
  .main__heading {
    font-size: 5rem;
    margin-top: 6rem;
  }
}

@media only screen and (min-width: 1100px) {
  .main__heading {
    font-size: 7rem;
    margin-top: 6rem;
  }
}
.file {
  margin-top: 2rem;
  position: relative;
  display: inline-block;
  cursor: pointer;
  height: 2.5rem;
}
.file input {
  min-width: 14rem;
  margin: 0;
  filter: alpha(opacity=0);
  opacity: 0;
}
.file-custom {
  position: absolute;
  top: 0;
  right: 0;
  left: 0;
  z-index: 5;
  height: 2.5rem;
  padding: 0.5rem 1rem;
  line-height: 1.5;
  color: #555;
  background-color: #fff;
  border: 0.075rem solid #ddd;
  border-radius: 0.25rem;
  box-shadow: inset 0 0.2rem 0.4rem rgba(0, 0, 0, 0.05);
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
}
.file-custom:after {
  font-family: "Roboto";
  content: "Choose file...";
}
.file-custom:before {
  position: absolute;
  top: -0.075rem;
  right: -0.075rem;
  bottom: -0.075rem;
  z-index: 6;
  display: block;
  content: "Browse";
  height: 2.5rem;
  padding: 0.5rem 1rem;
  line-height: 1.5;
  color: #555;
  background-color: #eee;
  border: 0.075rem solid #ddd;
  border-radius: 0 0.25rem 0.25rem 0;
}

.file input:focus ~ .file-custom {
  box-shadow: 0 0 0 0.075rem #fff, 0 0 0 0.2rem #0074d9;
}

.main__canvas {
  position: absolute;
}

canvas {
  position: absolute;
  top: 0;
  left: 0;
}