:root {
    --color--white: white;
    --color--gray: #C4C4C4;
    --color--green: #70ff70;
    --color--black: black;    
    --color--error: #ff7070;
    --border-radius: 1vmin;
}

:root.dark {
    --color--white: black;
    --color--black: #666666;
    --color--gray: #888888;
}

@keyframes fade-slide {
  from {
    opacity: 0.5;
    /* transform: translateY(50vh); */
    transform: rotate3d(0.5, 1, 0, 90deg);
}
  to {
    opacity: 1;
    transform: rotate3d(0, 0, 0, 0deg);
  }
}

@keyframes pulse {
  0%   { transform: scale(1); }
  50%  { transform: scale(1.5); }
  100% { transform: scale(1); }
}

#sudoku-grid {
  animation: fade-slide 1500ms ease-out forwards;
}

#control-pad {
    opacity: 1;
    /* animation: pulse 2000ms ease-out forwards; */
    transition: opacity 2000ms ease-out;
}

#control-pad.hidden {
    opacity: 0;
}

body {
    font-family: Arial, sans-serif;
    padding: 0;
    background: var(--color--white);
    margin: 0;
    text-align: center;
    transition: background-color 1s ease, color 0.2s ease;
}

#container {
    display: inline-grid;
    align-items: start;
    width: min-content;
    margin-top: 4vmin;
    /* width: fit-content;
    margin-left: auto;
    margin-right: auto; */
}

@media (orientation: landscape) {
  #container {
    grid-template-rows: auto auto;
    grid-template-columns: auto auto;
  }

  #display {
    grid-row-start: 1;
    grid-row-end: 2;
    grid-column-start: 2;
    grid-column-end: 3;
  }

  #sudoku-grid {
    grid-row-start: 1;
    grid-row-end: 3;
    grid-column-start: 1;
    grid-column-end: 2;
    margin: 0;
    margin-right: 1vmin;
  }

  #control-pad {
    grid-row-start: 2;
    grid-row-end: 3;
    grid-column-start: 2;
    grid-column-end: 3;
  }
}

@media (orientation: portrait) {
  #container {
    grid-template-columns: auto;
    grid-template-rows: auto auto auto;
  }

  #display {
    grid-row-start: 1;
    grid-row-end: 2;
  }

  #sudoku-grid {
    grid-row-start: 2;
    grid-row-end: 3;
    margin: 0;
    margin-top: 1vmin;
    margin-bottom: 1vmin;
  }

  #control-pad {
    grid-row-start: 3;
    grid-row-end: 4;
  }
}

#sudoku-grid {
    border: 3pt solid var(--color--black);
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    grid-template-rows: repeat(3, 1fr);
    gap: 0;
    font-size: 8vmin;
    line-height: 100%;
    width: fit-content;
    transition: background-color 500ms ease;

    /* transition: background-color 1s ease, transform 1s ease; */
}

#sudoku-grid.happy {
    background-color: var(--color--green);
    transform: scale(1.05);
    /* animation: pulse 3000ms ease-out forwards; */
    transition: background-color 1s ease;
}

.cell-group {
    border: 2pt solid var(--color--black);
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    grid-template-rows: repeat(3, 1fr);
    gap: 0;
    line-height: 100%;
}

.cell {
    display: flex;
    gap: 0;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    border: 1pt solid var(--color--black);
    /* background: var(--color--white); */
    font-size: 8.4vmin;
    font-weight: bold;
    line-height: 100%;
    width: 9.25vmin;
    height: 9.25vmin;
    /* transition: background-color 1s ease, transform 1s ease; */
}

.cell:hover {
    background: var(--color--black);
}

.cell.selected {
    background: #bbdefb;
}

.cell.certain {
    color: #1976d2;
}

.cell.locked {
    background: var(--color--gray);
    color: #000;
    font-weight: bold;
    cursor: not-allowed;
}

.cell.locked:hover {
    background: var(--color--gray);
}

.cell.error {
    background: var(--color--error);
    transform: scale(1.25);
    /* transition: background-color 1s ease, transform 1s ease; */
    animation: pulse 3000ms ease-out forwards;
    /* animation: pulse 2000ms ease-out forwards; */
}

.cell.hint {
    background: var(--color--green);
    animation: pulse 3000ms ease-out forwards;
}

.pencil-marks {
    display: grid;
    grid-template-columns: repeat(3, 2.0vmin);
    grid-template-rows: repeat(3, 2.0vmin);
    width: 100%;
    height: 100%;
    font-size: 2.5vmin;
    color: #666;
    justify-content: space-around;
    align-content: space-evenly;
}

.pencil-mark {
    display: flex;
    align-items: center;
    justify-content: center;
    line-height: 100%;
}
/* 
.cell:nth-child(3n) {
    border-right: 0.1em solid #000;
}

.cell:nth-child(n+19):nth-child(-n+27),
.cell:nth-child(n+46):nth-child(-n+54) {
    border-bottom: 0.1em solid #000;
}
*/

.pad {
    padding: 1vmin;
    background: var(--color--white);
    display: none;
    position: absolute;
    border-radius: var(--border-radius);
    box-shadow: 0 4px 20px rgba(0,0,0,0.3);
    z-index: 1000;
}

#difficulty-pad.active,
#number-pad.active {
    display: block;
}

.number-grid {
    display: inline-grid;
    justify-items: center;
    grid-template-columns: repeat(3, auto);
    gap: 1vmin;
    margin-bottom: 2vmin;
}

.number-btn,
.control-btn {
    background: var(--color--white);
    border-radius: var(--border-radius);
    padding: 0;
    margin: 0;
    border: 2pt solid #1976d2;
    color: #1976d2;
    cursor: pointer;
    font-weight: bold;
    -webkit-tap-highlight-color: rgba(0,0,0,0.1);
    touch-action: manipulation;
}

.number-btn:hover,
.control-btn:hover {
    background: #e3f2fd;
}

.number-btn[disabled],
.control-btn[disabled] {
    background: black;
}

.number-btn:active,
.control-btn:active {
    background: #e3f2fd;
}

.number-btn {
    width: 10vmin;
    height: 10vmin;
    font-size: 7vmin;
}

.control-btn {
    width: 8.5vmin;
    height: 8.5vmin;
    font-size: 6.5vmin;
}

.action-buttons {
    gap: 2vmin;
    display: grid;
    grid-template-columns: 1fr 1fr;
}

.action-btn {
    font-size: 7vmin;
    border: none;
    border-radius: var(--border-radius);
    cursor: pointer;
    font-weight: bold;
    white-space: nowrap;
}

.btn-certain {
    background: #1976d2;
    color: var(--color--white);
}

.btn-maybe {
    background: #4caf50;
    color: var(--color--white);
}

.btn-clear {
    background: #f44336;
    color: var(--color--white);
}

.btn-cancel {
    background: #757575;
    color: var(--color--white);
}

.action-btn:hover {
    opacity: 0.8;
}

#previous-game-button,
#next-game-button {
    width: 12vmin;
}

#overlay {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.5);
    z-index: 999;
}

#overlay.active {
    display: block;
}

.controls {
    display: grid;
    gap: 1vmin;
}

#display {
    display: flex;
    flex-wrap: wrap;
    align-content: space-around;
    align-items: center;
    /* display: grid;
    grid-template-rows: auto auto;
    grid-template-columns: auto auto; */
    padding: 0;
    margin: 0;
    font-size: 6vmin;
    background: black;
    color: var(--color--gray);
    text-align: center;
    border: 2pt solid var(--color--black);
    border-radius: var(--border-radius);
}

#display button {
    border: none;
    border-radius: 0;
    background: none;
    padding: 0 3vmin;
    margin: 0;
    color: inherit;
}

#game-navigate-pad {
    display: grid;
    grid-template-rows: auto auto;
    grid-template-columns: auto auto auto;
    line-height: 100%;
    grid-row-start: 1;
    grid-row-end: 2;
    grid-column-start: 1;
    grid-column-end: 4;
}

#previous-game-button {
    grid-row-start: 1;
    grid-row-end: 3;
    grid-column-start: 1;
    grid-column-end: 2;
    line-height: 100%;
}

#new-game-button {
    grid-row-start: 1;
    grid-row-end: 2;
    grid-column-start: 2;
    grid-column-end: 3;
    line-height: 100%;
}

#game-number-display {
    grid-row-start: 2;
    grid-row-end: 3;
    grid-column-start: 2;
    grid-column-end: 3;
    font-size: 0.4em;
    line-height: 100%;
}

#next-game-button {
    grid-row-start: 1;
    grid-row-end: 3;
    grid-column-start: 3;
    grid-column-end: 4;
    line-height: 100%;
}

@media (orientation: landscape) {
    #display {
        height: 20vmin;
        flex-direction: column;
        justify-content: center;
    }
    .controls {
        grid-template-columns: repeat(3, 1fr);
        grid-template-rows: auto;
    }
}

@media (orientation: portrait) {
    #display {
        height: 10vmin;
        flex-direction: row;
        justify-content: space-around;
    }
    .controls {
        grid-template-columns: repeat(9, 1fr);
        grid-template-rows: auto;
        justify-items: center;
    }
}

@media print {
    #display,
    .pad,
    button,
    .noprint {
        display: none !important;
    }
}

@media (prefers-reduced-motion: reduce) {
  * {
    animation: none !important;
    transition: none !important;
  }
}