html {
  background: #ccc;
}

body {
  font-family: sans-serif;
  font-weight: 400;
 
  width: 31.1rem;
  margin: auto;
  padding: 1rem 2rem;
  
  background: #fff;
}

.sudoku {
  display: grid;
  grid-template-columns: repeat(3, 3.2rem) 0.15rem repeat(3, 3.2rem) 0.15rem repeat(3, 3.2rem);
  grid-template-rows: repeat(3, 3.2rem) 0.15rem repeat(3, 3.2rem) 0.15rem repeat(3, 3.2rem);
  width: fit-content;

  gap: 0.1rem;
  place-items: center;
  
  padding: 0.5rem;
  margin: 1rem 0;
  background: #999;
}

.cell {
  width: 3rem;
  height: 3rem;
  background: #fff;
  color: #048;
}


.cell:not(.cell-fixed):focus,
.cell:not(.cell-fixed).focused {
  border: 0.25rem solid lightblue;
  margin: 0;
}

.cell.cell-fixed,
.cell.cell-single {
  font-size: 2.5rem;
  line-height: 3rem;
  text-align: center;
}

.cell.cell-fixed {
  color: #000;
  font-weight: bold;
}

.keyboard {
  display: grid;
  width: fit-content;
  margin: auto;
  grid-template-columns: repeat(6, 4rem);
}

.keyboard button {
  font-size: 2.0rem;
  grid-column: span 2;
  margin: 0.2rem 0.1rem;
  
  border: 2px solid #999;
  background: #eee;
}

.keyboard button.clear,
.keyboard button.notes {
  font-size: 1.5rem;
  grid-column: span 3;
}

button.notes.notes-active {
  background: darkgray;
}