* {
  box-sizing: border-box;
}

/**
 * Make the player's eyes blink.
 */
@keyframes blink {
  0%, 100% {
    transform: rotateX(0);
  }
  50% {
    transform: rotateX(90deg);
  }
}

:root {
  --tile-size: 3rem;
  --x: 0;
  --y: 0;
  background: #0f172a;
  color: #d1d5db;
  font-family: system-ui;
}

body, html {
  padding: 0;
  margin: 0;
}

body {
  height: 100vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  user-select: none;
}

main {
  display: flex;
  flex-direction: column;
}

game-header {
  display: flex;
  padding: 1.5rem;
  justify-content: center;
  margin-bottom: 0.5rem;
  gap: 2rem;
}

a,
select,
button {
  font: inherit;
  text-decoration: none;
  color: inherit;
  border: none;
  background: transparent;
  display: inline-flex;
  gap: 0.5rem;
  cursor: pointer;
  padding: 0.5rem 0.75rem;
  border-radius: 0.5rem;
  transition: background 0.15s;
}

select:hover,
button:hover {
  background: #0f172a;
  background: #334155;
  filter: brightness(125%);
  box-shadow: 0.25rem 0.25rem 0.5rem #020617;
}

button:active {
  background: #0f172a;
}

game-board {
  box-sizing: content-box;
  --width: 10;
  --height: 10;
  --bg: #334155;
  display: block;
  position: relative;
  margin: auto;
  width: calc(var(--width) * var(--tile-size));
  height: calc(var(--height) * var(--tile-size));
}

game-board:before {
  --offset: calc(var(--tile-size) / -4);
  position: absolute;
  content: '';
  background: var(--bg);
  background-image: linear-gradient(to bottom right, #475569, #64748b, #475569);
  border-radius: calc(var(--tile-size) / 4);
  box-shadow: 0.5rem 0.5rem 2rem #020617;
  top: var(--offset);
  left: var(--offset);
  bottom: var(--offset);
  right: var(--offset);
}

.win game-board:before {
  background: #475569;
  opacity: 0.5;
}

game-shape {
  position: absolute;
  left: calc(var(--x) * var(--tile-size));
  top: calc(var(--y) * var(--tile-size));
  transition: filter 0.2s;
}

game-slot,
game-gap,
game-block {
  position: absolute;
  width: var(--tile-size);
  height: var(--tile-size);
  left: calc(var(--x) * var(--tile-size));
  top: calc(var(--y) * var(--tile-size));
}

game-block {
  --shadowA: inset 1px 1px 0 1px rgba(255 255 255 / 0.25);
  --shadowB: inset -1px -1px 0 1px rgba(0 0 0 / 0.25);
  box-shadow: var(--shadowA), var(--shadowB);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  background: var(--bg);
  cursor: move;
}

game-shape:hover {
  z-index: 40;
  filter: brightness(1.2);
  cursor: pointer;
}

game-slot {
  --bg: #020617;
  --bg: rgba(0 0 20 / 0.5);
  --rounded: calc(var(--tile-size) / 8);
  background: var(--bg);
  border: 4px solid transparent;
}

.block-0 {
  --bg: #0284c7;
}

.block-1 {
  --bg: #eab308;
}

.block-2 {
  --bg: #16a34a;
}

.block-3 {
  --bg: #6d28d9;
}

.block-4 {
  --bg: #be123c;
}

.block-5 {
  --bg: #a21caf;
}

.block-6 {
  --bg: #64748b;
}

game-shape {
  z-index: 10;
}

game-shape.illegal game-block:after,
game-shape.active game-block:after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  box-shadow: 0 0 0 2px rgba(255 255 255 / 0.75);
}

game-shape.active game-block {
  box-shadow: var(--shadowA), var(--shadowB),
    1rem 1rem 1rem rgba(0 0 0 / 0.5);
}

game-shape.illegal game-block {
  box-shadow: var(--shadowA), var(--shadowB),
    1rem 1rem 1rem rgba(0 0 0 / 0.5);
}

game-shape.illegal game-block:after {
  box-shadow: 0 0 0 2px rgba(255 0 0 / 0.75);
}

.hidden {
  visibility: hidden;
}

.illegal {
  z-index: 30;
}

.active {
  z-index: 50;
}

@keyframes blockwin {
  0% {
  }
  25% {
    --bg: #fff;
    background: var(--bg);
    box-shadow: 0 0 1rem var(--bg);
  }
  50% {
    box-shadow: none;
  }
  100% {
    --bg: transparent;
    background: var(--bg);
    box-shadow: none;
  }
}

.win game-block {
  animation: blockwin 1s forwards;
}

.win game-slot {
  opacity: 0.5;
}

.btn-next {
  transition: all 0.2s;
}

.btn-next:hover,
.win .btn-next {
  background: #065f46;
  color: #a7f3d0;
}

.btn-next:hover {
  filter: brightness(150%);
}

.win .btn-next {
  display: inline-flex;
}