:root {
  --primary-color: 74, 144, 226;
  --error-color: 231, 76, 60;
}

body {
  font-family: Arial, sans-serif;
  background-color: color-mix(in hsl, rgb(var(--primary-color)), #c6f2fa 75%);
  margin: 0;
  padding: 20px;
}

h1 {
  color: #333;
  text-align: center;
  margin-bottom: 50px;
  font-size: 2.5em;
}

main {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 30px;
}

#sudoku {
  display: grid;
  grid-template-columns: repeat(9, 50px);
  grid-template-rows: repeat(9, 50px);
  gap: 1px;
  background-color: #333;
  border: 2px solid #333;
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

#sudoku>div {
  display: contents;
}

.cell {
  width: 50px;
  height: 50px;
  background-color: #fff;
  border: none;
  font-size: 1.5em;
  text-align: center;
  cursor: pointer;
  color: rgb(var(--primary-color));
  transition: background-color 0.2s;
}

.cell.locked {
  color: black !important;
  pointer-events: none;
}

.cell.victory {
  color: rgb(146, 255, 113) !important;
  pointer-events: none;
}

.cell.fail {
  color: rgb(255, 122, 122) !important;
  pointer-events: none;
}

.cell.highlight {
  background-color: color-mix(in srgb, rgb(var(--primary-color)), #fff 75%);
}

.cell:hover {
  background-color: color-mix(in hsl, rgb(var(--primary-color)), #fff 75%);
  ;
}

.cell:focus {
  background-color: color-mix(in srgb, rgb(var(--primary-color)), #fff 50%) !important;
  outline: none;
}

.cell.error {
  background-color: color-mix(in srgb, rgb(var(--error-color)), #fff 50%) !important;
  color: rgb(var(--error-color));
}

#sudoku>div>.cell:nth-child(3n) {
  border-right: 2px solid #333;
}

#sudoku>div:nth-child(3n)>.cell {
  border-bottom: 2px solid #333;
}

#keyboard {
  display: grid;
  grid-template-rows: repeat(4, 50px);
  grid-template-columns: repeat(4, 50px);
  gap: 10px;
  margin-top: 20px;
}

#keyboard button {
  background-color: rgb(var(--primary-color));
  color: #fff;
  border: none;
  font-size: 1.5em;
  cursor: pointer;
  border-radius: 5px;
  transition: background-color 0.2s;
}

#keyboard button:hover {
  background-color: color-mix(in srgb, rgb(var(--primary-color)), #000 33%);
}

#keyboard button:active {
  background-color: color-mix(in srgb, rgb(var(--primary-color)), #fff 33%);
}

#keyboard #erase {
  grid-row: 1 / 4;
  grid-column: 4 / 4;
}

#keyboard #restart {
  grid-row: 4 / 4;
  grid-column: 1 / 5;
}

#keyboard #restart {
  padding: 10px 20px;
  background-color: rgb(var(--error-color));
  color: #fff;
  border: none;
  border-radius: 5px;
  font-size: 1.2em;
  cursor: pointer;
  transition: background-color 0.2s;
}

#keyboard #restart:hover {
  background-color: color-mix(in srgb, rgb(var(--error-color)), #000 33%);
}

#keyboard #restart:active {
  background-color: color-mix(in srgb, rgb(var(--error-color)), #fff 33%);
}

@media (max-width: 600px) {
  #sudoku {
    grid-template-columns: repeat(9, 40px);
    grid-template-rows: repeat(9, 40px);
  }

  .cell {
    width: 40px;
    height: 40px;
    font-size: 1.2em;
  }

  #keyboard div {
    grid-template-columns: repeat(3, 40px);
  }

  #keyboard input {
    width: 40px;
    height: 40px;
    font-size: 1.2em;
  }

  h1 {
    font-size: 2em;
  }
}