sudoku.css

* {
  border: none;
  margin: 0;
  padding: 0;
}

:root {
  --default-font-family: unset;
  --main-font-family: var(--default-font-family, 'system-ui');
  --digit-font-family: 'Arial';

  --size-1vmin: clamp(3.6px, 1vmin, 4.2px);

  --size-0_5vmin: calc(var(--size-1vmin) * 0.5);
  --size-1_5vmin: calc(var(--size-1vmin) * 1.5);
  --size-2vmin:   calc(var(--size-1vmin) * 2);
  --size-2_5vmin: calc(var(--size-1vmin) * 2.5);
  --size-3vmin:   calc(var(--size-1vmin) * 3);
  --size-4vmin:   calc(var(--size-1vmin) * 4);
  --size-5vmin:   calc(var(--size-1vmin) * 5);
  --size-6vmin:   calc(var(--size-1vmin) * 6);
  --size-8vmin:   calc(var(--size-1vmin) * 8);
  --size-10vmin:  calc(var(--size-1vmin) * 10);

  --size-1vmax: clamp(6.4px, 1vmax, 9px);
}

a, a:hover, a:visited {
  color: #cccccc;
  text-decoration: underline dotted;
}

body {
  position: static;
  z-index: 0;
}

button {
  cursor: pointer;
}

.hidden {
  display: none !important;
}

.no-wrap {
  white-space: nowrap;
}

.header {
  width: calc(var(--size-1vmin) * 96);
  margin: var(--size-1vmax) auto 0 auto;
  margin-bottom: calc(var(--size-1vmax) * 0.8);
}

.header > div {
  background: #f2f2f2;
  display: flex;
  margin-left: 0;
  margin-right: var(--size-2vmin);
}

.header > div > div {
  position: relative;
  margin-top: auto;
  margin-bottom: auto;
  flex: 1 1 0;
}
.header > div > :first-child {
  text-align: left;
}
.header > div > :not(:first-child):not(:last-child) {
  text-align: center;
}
.header > div > :last-child {
  text-align: right;
}

.header select {
  background: #f2f2f2;
  color: navy;
  font: bold var(--size-4vmin) var(--main-font-family);
  width: calc(var(--size-1vmin) * 31);
}

.header .center {
  overflow: hidden;
}
.header .center > div {
  position: relative;
}
.header .center > .slide-up {
  transform: translateY(-100%);
  transition: transform 1s ease-in-out;
}

.header .title {
  font: bold calc(var(--size-1vmin) * 4.5) var(--main-font-family);
}
.header .game-selection {
  color: navy;
  font: normal var(--size-4vmin) var(--main-font-family);
  overflow: hidden;
  text-overflow: clip;
  white-space: nowrap;
}

.header .buttons {
  display: flex;
  justify-content: space-evenly;
}
.header .buttons > button {
  display: block;
  padding: 0 var(--size-1_5vmin) var(--size-0_5vmin) var(--size-1_5vmin);

  border: 1px outset #eaeaea;
  border-radius: clamp(3.6px, 1vmin, 4.2px);
}
.header .buttons > :first-child {
  margin: 0 auto 0 0 !important;
}
.header .buttons > :not(:first-child):not(:last-child) {
  margin-left: auto;
  margin-right: auto;
  text-align: center;
}
.header .buttons > :last-child {
  margin: 0 0 0 auto !important;
}

@font-face {
  font-family: 'Digital-7 Mono';
  src: url('fonts/digital-7.mono.ttf');
}

.header .buttons > .timer {
  display: inline-block;
  font: normal calc(var(--size-1vmin) * 4.5) 'Digital-7 Mono';
  margin: auto;
}

.header .buttons > button::after {
  display: inline-block;
  font: normal var(--size-4vmin) var(--main-font-family);
}
.header .restart::after {
  /* U+21BB ↻*/
  content: '↻';
}
.header .settings::after {
  /* U+2699 ⚙ */
  content: '⚙';
}

.board {
  width: calc(var(--size-1vmin) * 98);
  margin: 0 auto;
}

.grid {
  padding-left: calc(var(--size-1vmin) * 1.6);
  width: 100%;
  text-align: center;
}

.grid .row {
  display: flex;
}

.grid .cell {
  aspect-ratio: 1 / 1;
  border: solid lightgrey;
  border-width: 1px 0 0 1px;
  position: relative;
  width: var(--size-10vmin);
}

.grid .cell.focused {
  z-index: 1;
  outline: auto #6666ff;
}
.grid .cell.same {
  background-color: #ffccff;
}

.grid .cell .value.if-1st,
.assumption.if-1st {
  background-color: #ccffcc;
}
.grid .cell .value.if-2nd,
.assumption.if-2nd {
  background-color: #ccccff;
}
.grid .cell .value.if-3rd,
.assumption.if-3rd {
  background-color: #ffcccc;
}

.grid .row-1 .cell,
.grid .row-1 .y-axis {
  border-top-width: 2px !important;
}

.grid .row-3 .cell, .grid .row-6 .cell {
  border-bottom-width: 1px !important;
}

.grid .row-9 .cell {
  border-bottom-width: 2px !important;
}

.grid .col-A {
  border-left-width: 2px !important;
}

.grid .col-C, .grid .col-F {
  border-right-width: 1px !important;
}

.grid .col-I {
  border-right-width: 2px !important;
}

.cell-A1, .cell-B1, .cell-C1,
.cell-A2, .cell-B2, .cell-C2,
.cell-A3, .cell-B3, .cell-C3,
.cell-D4, .cell-E4, .cell-F4,
.cell-D5, .cell-E5, .cell-F5,
.cell-D6, .cell-E6, .cell-F6,
.cell-G7, .cell-H7, .cell-I7,
.cell-G8, .cell-H8, .cell-I8,
.cell-G9, .cell-H9, .cell-I9 {
  background-color: #efffef;
}

.cell-D1, .cell-E1, .cell-F1,
.cell-D2, .cell-E2, .cell-F2,
.cell-D3, .cell-E3, .cell-F3,
.cell-G4, .cell-H4, .cell-I4,
.cell-G5, .cell-H5, .cell-I5,
.cell-G6, .cell-H6, .cell-I6,
.cell-A7, .cell-B7, .cell-C7,
.cell-A8, .cell-B8, .cell-C8,
.cell-A9, .cell-B9, .cell-C9 {
  background-color: #ffefff;
}

.cell-G1, .cell-H1, .cell-I1,
.cell-G2, .cell-H2, .cell-I2,
.cell-G3, .cell-H3, .cell-I3,
.cell-A4, .cell-B4, .cell-C4,
.cell-A5, .cell-B5, .cell-C5,
.cell-A6, .cell-B6, .cell-C6,
.cell-D7, .cell-E7, .cell-F7,
.cell-D8, .cell-E8, .cell-F8,
.cell-D9, .cell-E9, .cell-F9 {
  background-color: #efefff;
}

.grid .cell .value {
  font: normal var(--size-6vmin) var(--digit-font-family);
  position: relative;
  top: 50%;
  margin: auto;
  width: 88%;
  transform: translateY(-50%);
}

.grid .cell .value.given {
  color: black;
  font-weight: bold;
}

.grid .cell .value.pending {
  font: normal var(--size-4vmin) var(--digit-font-family);
  color: grey;
  position: relative;
  top: 28%;
}

.grid .cell .value.solved {
  color: blue;
}

.grid .cell .eliminated:not(:empty)::before {
  content: '-';
}
.grid .cell .eliminated {
  font: normal calc(var(--size-1vmin) * 3.2) var(--digit-font-family);
  color: #999999;
  position: relative;
  top: 10%;
}

.grid .cell .cross {
  background-color: #ffccff;
  position: absolute;
  margin: auto;
  z-index: 1;
}
.grid .cell .cross.row {
  left: 6%;
  top: 45%; /* 50% - (1vmin / 10vmin) / 2 */
  width: 88%;
  height: var(--size-1vmin);
}
.grid .cell .cross.column {
  left: 45%; /* 50% - (1vmin / 10vmin) / 2 */
  top: 6%;
  width: var(--size-1vmin);
  height: 88%;
}

.grid .coord {
  border: solid white;
  border-width: 1px 0 0 1px;

  color: lightgrey;
  font: bold calc(var(--size-1vmin) * 3.2) var(--main-font-family);
}

.grid .x-axis .coord {
  width: var(--size-10vmin);
}

.grid .y-axis {
  aspect-ratio: 1 / 4;
  text-align: left;
}

.grid .y-axis .value {
  position: relative;
  top: 50%; left: 25%;
  transform: translateY(-50%);
}

.keys {
  display: flex;
  justify-content: space-around;
  margin: var(--size-3vmin) auto 0 auto;
  padding-right: 1%;
  width: 97%;
  text-align: center;
}
.keys > :last-child {
  margin-left: var(--size-2vmin) !important;
}

.keys .key {
  aspect-ratio: 1 / 1;
  width: var(--size-8vmin);
  position: relative;
  margin: var(--size-0_5vmin);

  border: 1px outset #eaeaea;
  border-radius: var(--size-1vmin);

  color: grey;
  font: normal calc(var(--size-1vmin) * 6.5) var(--digit-font-family);
  cursor: pointer;
}
.keys .key.key-mode-ctrl {
  aspect-ratio: 5 / 4;
  width: calc(var(--size-1vmin) * 6.4);
}

.keys .key.key-mode-ctrl > div {
  font: normal var(--size-4vmin) var(--digit-font-family);
  position: absolute;
  z-index: 1;
}
.keys .key.key-mode-ctrl .value.from-mode {
  top: var(--size-2_5vmin);
  left: calc(var(--size-1vmin) * 0.3);
}
.keys .key.key-mode-ctrl .symbol {
  color: #990099;
  top: var(--size-2_5vmin);
  left: calc(var(--size-1vmin) * 0.8);
}
.keys .key.key-mode-ctrl .value.to-mode {
  bottom: var(--size-2_5vmin);
  right: calc(var(--size-1vmin) * 0.3);
}

.keys .key .value {
  position: relative;
  top: 50%;
  transform: translateY(-50%);
}

.keys.eliminating :not(:last-child) .value,
.keys.eliminating .value.from-mode,
.keys:not(.eliminating) .value.to-mode {
  text-decoration: 1px line-through red;
}

.keys .key.candidate {
  outline: auto #6666ff;
}

.keys .key .count {
  position: absolute;
  z-index: 1;
  bottom: 0;
  padding: 0 0 1px 2px;

  font-size: var(--size-3vmin);
  color: #990099;
  text-align: left;
}
.keys.eliminating .key .count {
  display: none;
}

.commands {
  margin: var(--size-3vmin) auto 0 auto;
  padding-right: 2%;
  width: 92%;
  text-align: center;
}

.commands .buttons {
  display: flex;
  justify-content: space-evenly;
  white-space: nowrap;
}
.commands .buttons > button {
  font: normal var(--size-4vmin) var(--main-font-family);
}
.commands .buttons > :first-child {
  margin-right: auto;
  text-align: left;
}
.commands .buttons > :not(:first-child):not(:last-child) {
  margin-left: auto;
  margin-right: auto;
  text-align: center;
}
.commands .buttons > :last-child {
  margin-left: auto;
  text-align: right;
}

.commands #undo::before {
  content: '⎌'
}
.commands #givens-filled {
  color: navy;
  font-weight: bold;
}
.commands #clean::after {
  content: '⌫'
}

.commands .block {
  display: block;
  margin: var(--size-1vmin);
  padding: var(--size-1vmin) var(--size-2vmin);
}

.commands .border {
  border: 1px outset #eaeaea;
  border-radius: var(--size-1vmin);
}

.commands .pending .assumption {
  display: flex;
  text-align: left;

  border: 1px solid #eaeaea;
  width: auto;
}

.commands .pending .assumption > * {
  font: normal var(--size-4vmin) var(--main-font-family);
}

.commands .pending .assumption button {
  display: block;
  margin: var(--size-1vmin);
  padding: 0 var(--size-1_5vmin) var(--size-0_5vmin) var(--size-1_5vmin);

  border: 1px outset #eaeaea;
  border-radius: var(--size-1vmin);
}
.commands .pending .assumption button::after {
  content: '';
  display: inline-block;
  background: border-box center/125% no-repeat;
  position: relative;
  top: 25%;
  width: var(--size-4vmin);
  height: var(--size-4vmin);
}

.commands .pending .assumption.first button[data-action="accept"]::after {
  background-image: none;
}
.commands .pending .assumption button[data-action="accept"]::after {
  /* U+2B73 ⭳ */
  background-image: url('images/U2B73.down-arrow-to-bar.png');
}
.commands .pending .assumption button[data-action="reject"]::after {
  /* U+21A7 ↧ */
  background-image: url('images/U21A7.down-arrow-from-bar.png');
}
.commands .pending .assumption.last button[data-action="reject"]::after {
  background-image: none;
}

.commands .pending .assumption .block {
  margin: 1px 2px;
  text-align: left;
}
.commands .pending .assumption > :first-child {
  flex: 1.6;
}
.commands .pending .assumption > :not(:first-child) {
  flex: 1;
}

.commands .tentative select {
  margin: auto;
  background: #f2f2f2;
}

.footer {
  position: absolute;
  width: 100%;
  margin: var(--size-0_5vmin) auto;
  text-align: center;
  font: var(--size-3vmin) var(--main-font-family);
  color: #d0d0d0;
  top: 96dvh;
}

.overlay {
  z-index: 10; position: absolute;
  top: 0; left: 0;
  width: 100vw; height: 100vh;
  background-color: white;
  opacity: 1;
}

.settings-view {
  width: calc(var(--size-1vmin) * 94);
  margin: 0 auto;
}

.settings-header {
  padding: var(--size-3vmin) 0;
  border-bottom: 2px solid lightgrey;
  font: bold var(--size-5vmin) var(--main-font-family);
}
.settings-header > span:not(:first-child) {
  margin-left: var(--size-8vmin);
}
.settings-header .go-back::before {
  /* U+1F860 🡠, U+1F868 🡨, U+1F870 🡰 */
  content: '';
  display: inline-block;
  position: absolute;
  background: border-box 50% 0 / 125% no-repeat url('images/U1F860.left-arrow.png');
  width: var(--size-6vmin);
  height: var(--size-6vmin);
  cursor: pointer;
}

.settings-content,
.settings-content select {
  background: white;
  font: normal var(--size-4vmin) var(--main-font-family);
  text-align: right;
}
.settings-content select#auxiliary-features {
  width: 70%;
}

.settings-content > div {
  padding: var(--size-2vmin) 0;
  border-bottom: 1px solid lightgrey;
  display: inline-flex;
  width: 100%;
}
.settings-content > div.level-1 > label {
  font-weight: bold;
}
.settings-content > div.level-2 {
  margin-left: var(--size-3vmin);
  width: calc(100% - var(--size-3vmin));
  border-bottom: 1px dotted lightgrey;
}
.settings-content > div.level-2.last {
  border-bottom: none;
}
.settings-content > div > * {
  display: inline-block;
  white-space: nowrap;
}
.settings-content > div > :last-child {
  margin-left: auto;
}

.switch {
  appearance: none;
  -webkit-tap-highlight-color: transparent;
  cursor: pointer;

  --switch-size: var(--size-5vmin);
  --switch-edge: var(--size-0_5vmin);

  height: var(--switch-size);
  width: calc(var(--switch-size) * 1.8);
  border-radius: calc(var(--switch-size) / 2);
  border: none;
  display: inline-block;
  position: relative;
  margin: 0;
  background: lightgrey;
  transition: all .2s ease;
}
.switch:after {
  content: '';
  position: absolute;
  top: var(--switch-edge);
  left: var(--switch-edge);
  width: calc(var(--switch-size) - var(--switch-edge) * 2);
  height: calc(var(--switch-size) - var(--switch-edge) * 2);
  border-radius: 50%;
  background: white;
  transition: all .2s cubic-bezier(.5,.1,.75,1.35);
}
.switch:checked {
  background: #3333ff;
}
.switch:checked:after {
  transform: translateX(calc(var(--switch-size) * 0.8));
}

.settings-footer {
  font: normal var(--size-4vmin) var(--main-font-family);
  padding: var(--size-3vmin) 0;
  border-top: 1px solid lightgrey;
  width: 100%;
}
.settings-footer div.label > span {
  font-weight: bold;
}
.settings-footer div.qrcode {
  margin-top: 1vmin;
  text-align: center;
}
.settings-footer > div.app {
  color: #cccccc;
  font: var(--size-3vmin) var(--main-font-family);
  text-align: center;
}
.settings-footer > div.app > #upgrade {
  border: 1px outset darkgray;
  border-radius: 1vmin;
  background-color: var(--button-color);
  color: green;
  padding: 0.5vmin 1vmin;
  margin-bottom: 0.5vmin;
}