style.css

html {
  font-family: sans-serif;
  user-select: none;
}

body {
  max-width: 1100px;
  margin: auto;
}

h1 {
  text-align: center;
  font-size: 30pt;
}

.form {
  margin: 1em 0;
}

#cards {
  font-size: 14pt;
  display: flex;
  flex-direction: column;
  flex-wrap: wrap;
  max-height: 550px;
}

#cards table {
  width: 48%;
  margin: 10px 1%;
  border-spacing: 0;
  border-collapse: collapse;
  border: 10px solid lightblue;
}

#cards td {
  margin: 0;
  padding: 5px;
  width: 30px;
  height: 30px;
  border: 1px solid grey;
  line-height: 1.6em;
  text-align: center;
  cursor: pointer;
}

#cards td.blank {
  background-color: #eee;
  cursor: default;
}

#cards td.called {
  background-color: green;
  color: white;
}

#footer {
  margin-top: 1em;
}
#footer ul {
  list-style: none;
  line-height: 1.5em;
}

@media only print {
  #cards {
    max-height: 500px;
  }

  #cards table {
    width: 48%;
    font-size: 12pt;
    border-spacing: 0;
  }

  #cards td {
    margin: 0;
    padding: 3px;
    line-height: 1.5em;
    border: 1px solid grey;
    width: 24px;
    height: 24px;
  }

  #cards td.blank {
    background-color: default;
  }

  #cards td.called {
    background-color: default;
    color: default;
  }

  #footer {
    display: none;
  }
}

@media only screen and (max-width: 1000px) {
  h1 {
    font-size: 36pt;
  }

  #cards {
    font-size: 36pt;
    flex-wrap: nowrap;
  }

  #cards table {
    margin: 10px 1%;
    width: 98%;
    border-width: 20px;
  }

  #cards td {
    line-height: 1.6em;
    width: 80px;
    height: 80px;
    border-width: 2px;
  }
}

@media only screen and (max-width: 950px) {
  h1 {
    font-size: 34pt;
  }

  #cards {
    font-size: 34pt;
  }

  #cards table {
    border-width: 20px;
  }

  #cards td {
    width: 75px;
    height: 75px;
  }
}

@media only screen and (max-width: 900px) {
  h1 {
    font-size: 32pt;
  }

  #cards {
    font-size: 32pt;
  }

  #cards table {
    border-width: 20px;
  }

  #cards td {
    width: 72px;
    height: 72px;
  }
}

@media only screen and (max-width: 850px) {
  h1 {
    font-size: 30pt;
  }

  #cards {
    font-size: 30pt;
  }

  #cards table {
    border-width: 18px;
  }

  #cards td {
    width: 70px;
    height: 70px;
    border-width: 1px;
  }
}

@media only screen and (max-width: 800px) {
  h1 {
    font-size: 28pt;
  }

  #cards {
    font-size: 28pt;
  }

  #cards table {
    border-width: 16px;
  }

  #cards td {
    width: 65px;
    height: 65px;
  }
}

@media only screen and (max-width: 750px) {
  h1 {
    font-size: 26pt;
  }

  #cards {
    font-size: 26pt;
  }

  #cards table {
    border-width: 14px;
  }

  #cards td {
    width: 60px;
    height: 60px;
  }
}

@media only screen and (max-width: 700px) {
  h1 {
    font-size: 24pt;
  }

  #cards {
    font-size: 24pt;
  }

  #cards table {
    border-width: 14px;
  }

  #cards td {
    width: 54px;
    height: 54px;
  }
}

@media only screen and (max-width: 650px) {
  h1 {
    font-size: 22pt;
  }

  #cards {
    font-size: 22pt;
  }

  #cards table {
    border-width: 12px;
  }

  #cards td {
    width: 48px;
    height: 48px;
  }
}

@media only screen and (max-width: 600px) {
  h1 {
    font-size: 20pt;
  }

  #cards {
    font-size: 20pt;
  }

  #cards table {
    border-width: 12px;
  }

  #cards td {
    padding: 2px;
    width: 50px;
    height: 50px;
  }
}

@media only screen and (max-width: 550px) {
  h1 {
    font-size: 18pt;
  }

  #cards {
    font-size: 18pt;
  }

  #cards table {
    border-width: 14px;
  }

  #cards td {
    width: 45px;
    height: 45px;
  }
}

@media only screen and (max-width: 500px) {
  h1 {
    font-size: 18pt;
  }

  #cards {
    font-size: 18pt;
  }

  #cards table {
    border-width: 10px;
  }

  #cards td {
    width: 40px;
    height: 40px;
  }
}

@media only screen and (max-width: 450px) {
  h1 {
    font-size: 16pt;
  }

  #cards {
    font-size: 16pt;
  }

  #cards table {
    border-width: 10px;
  }

  #cards td {
    width: 30px;
    height: 30px;
  }
}

@media only screen and (max-width: 400px) {
  h1 {
    font-size: 14pt;
  }

  #cards {
    font-size: 14pt;
  }

  #cards table {
    border-width: 10px;
  }

  #cards td {
    line-height: 1.5em;
    width: 29px;
    height: 29px;
  }
}

@media only screen and (max-width: 350px) {
  h1 {
    font-size: 12pt;
  }

  #cards {
    font-size: 12pt;
  }

  #cards table {
    border-width: 10px;
  }

  #cards td {
    width: 24px;
    height: 24px;
  }
}

@media only screen and (max-width: 300px) {
  h1 {
    font-size: 10pt;
  }

  #cards {
    font-size: 10pt;
  }

  #cards table {
    width: 99%;
    margin: 6px 0.5%;
    border-width: 8px;
  }

  #cards td {
    line-height: 1.3em;
    width: 18px;
    height: 18px;
  }
}

@media only screen and (max-width: 250px) {
  h1 {
    font-size: 8pt;
  }

  #cards {
    font-size: 8pt;
  }

  #cards table {
    margin: 5px 0.5%;
    border-width: 6px;
  }

  #cards td {
    padding: 1px;
    line-height: 1.1em;
    width: 14px;
    height: 14px;
  }
}