sudoku.css

input {
  margin: 0px 0px 0px 0px;
  width: 34px;
  height: 34px;
  border: none;
  text-align: center;
  font-size: 18px;
}

#solve_button{
  margin-top: 10px;
  width: 100px;
}

#table_container td {
  width: 40px;
  height: 40px;
  text-align: center;
  font-size: 18px;
}

#table_container td {
  text-align: center;
  font-size: 18px;
}

#td4, #td7, #td13, #td16, #td22, #td25, #td31, #td34, #td40, #td43, #td49, #td52, #td58, #td61, #td67, #td70, #td76, #td79 {
  border-left: 3px solid black;
}

#tr3, #tr6 {
  border-top: 3px solid black;
}