style.css

:root {
  --first-color: #F8D540;
  --second-color: DimGrey;
  --third-color: Gainsboro;
  --fourth-color: rgb(243, 242, 242);
  --fifth-color: #2AB8E2;
}

body {
  width: 100vw;
  height: 100vh;
  background-color: var(--first-color);
  font-family: "Lato", sans-serif;
  font-size: 15px;
}

#container {
  display: flex;
  flex-direction: column;
  color: var(--second-color);
  margin: 50px auto;
  width: 360px;
  height: 600px;
  background: var(--fourth-color);
  box-shadow: 5px 5px 5px var(--third-color);
  border-radius: 20px;
  padding-bottom: 20px;
}

.page-title {
  background: var(--third-color);
  color: var(--second-color);
  padding: 30px;
  text-transform: uppercase;
  font-size: 18px;
  font-weight: normal;
  border-top-left-radius: 20px;
  border-top-right-radius: 20px;
  text-align: center;
}

.page-subtitle {
  color: var(--second-color);
  padding: 20px;
  font-size: 15px;
  font-weight: normal;
  text-align: center;
}

.grades-form {
  display: flex;
  flex-direction: column;
  align-items: center;
}

.grades-form > label {
  margin: 5px;
  color: var(--second-color); 
}

.form-input {
  background: #fff;
  width: 100px;
  padding: 5px 5px 8px 8px;
}

.form-input:focus {
  border: 3px solid var(--first-color);
  outline: none;
}

.form-select {
  width: 180px;
  padding: 5px;
  font-size: 12px;
}

.form-submit {
  display: block;
  font-weight: 700;
  margin: 30px auto;
  text-transform: uppercase;
  background-color: var(--fifth-color);
  border-radius: 5px;
  width: 200px;
  height: 50px;
  font-size: 17px;
  color: #fff;
}

.result-banner {
  display: block;
  text-align: center;
  color: black;
  font-size: 18px;
}