* {
  border: 0;
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
:root {
  font-size: calc(16px + (20 - 16) * (100vw - 320px) / (1024 - 320));
}
body,
button {
  color: #fff;
  font: 1em Muli, "Helvetica Neue", Helvetica, sans-serif;
  line-height: 1.5;
}
body {
  overflow: hidden;
}
button,
canvas {
  -webkit-tap-highlight-color: transparent;
}
button,
.difficulty-select,
.tutorial {
  opacity: 0;
}
button {
  background: #27dbf3;
  border-radius: 0.375em;
  box-shadow: 0 0 0 0.25em inset, 0 -0.5em 0 #0003 inset;
  cursor: pointer;
  display: block;
  font-weight: 700;
  margin: 0 auto 0.75em auto;
  padding: 0.75em 1.5em;
  transition: background 0.15s linear;
  transform: translateY(50%);
  width: 100%;
  max-width: 16em;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
}
button:hover {
  background: #1b7885;
}
button:active {
  background: #27dbf3;
}
button:disabled {
  cursor: default;
}
header,
.difficulty-select,
.tutorial,
.replay {
  position: absolute;
  z-index: 1;
}
header,
.difficulty-select {
  left: 0;
  width: 100%;
}
header,
h1 {
  line-height: 1;
}
header {
  font-size: 4em;
  font-weight: 900;
  top: 0;
  padding: 0.75rem;
  -webkit-text-stroke: 4px #171717;
  text-shadow: 0 4px 0 #171717;
  transform: translateY(-100%);
  transition: all 0.25s linear;
}
h1 {
  font-size: 2em;
  margin-bottom: 1em;
  text-align: center;
  transform: translateX(100%);
}
kbd {
  background: #242424;
  border-radius: 0.25em;
  display: inline-block;
  font-family: Helvetica, sans-serif;
  height: 1.5em;
  min-width: 1.5em;
  padding: 0 0.25em;
  text-align: center;
  vertical-align: middle;
}
p {
  margin-bottom: 1.5em;
}

/* UI */
.difficulty-select,
.tutorial,
.replay {
  top: 50%;
}
.difficulty-select,
.tutorial {
  background: #0000007f;
}
.difficulty-select {
  padding: 1.5em 0;
  transform: translateY(-50%);
}
.menu-active,
.tutorial-active,
.replay-active {
  z-index: 9;
}
.menu-active {
  animation: fadeIn 0.5s linear forwards;
}
.menu-active h1 {
  animation: slideIn 0.5s 0.5s linear forwards;
}
.menu-active button:nth-of-type(1) {
  animation: fadeSlide 0.15s 1s linear forwards;
}
.menu-active button:nth-of-type(2) {
  animation: fadeSlide 0.15s 1.15s linear forwards;
}
.menu-active button:nth-of-type(3) {
  animation: fadeSlide 0.15s 1.3s linear forwards;
}
.menu-active button:nth-of-type(4) {
  animation: fadeSlide 0.15s 1.45s linear forwards;
}
.menu-inactive {
  animation: fadeIn 0.5s 1.1s linear reverse forwards;
  opacity: 1;
}
.menu-inactive h1 {
  animation: slideOut 0.5s 0.6s linear forwards;
  transform: translateX(0);
}
.menu-inactive button {
  opacity: 1;
  transform: translateY(0);
}
.menu-inactive button:nth-of-type(1) {
  animation: fadeSlide 0.15s linear reverse forwards;
}
.menu-inactive button:nth-of-type(2) {
  animation: fadeSlide 0.15s 0.15s linear reverse forwards;
}
.menu-inactive button:nth-of-type(3) {
  animation: fadeSlide 0.15s 0.3s linear reverse forwards;
}
.menu-inactive button:nth-of-type(4) {
  animation: fadeSlide 0.15s 0.45s linear reverse forwards;
}
.tutorial {
  border-radius: 0.75em;
  padding: 1.5em 1.5em 0 1.5em;
  left: 50%;
  text-align: center;
  width: 12em;
  transform: translate(-50%, -50%);
  transition: opacity 0.25s linear;
}
.replay {
  margin: 0;
  padding: 1.5em;
  left: 50%;
  transform: translate(-50%, 0);
  transition: all 0.15s linear;
  width: 6em;
  height: 6em;
}
.btn-icon {
  fill: #fff;
  width: 3em;
  height: 3em;
}
.score-active {
  transform: translateY(0);
}
.tutorial-active,
.replay-active {
  opacity: 1;
}
.replay-active {
  transform: translate(-50%, -50%);
}

/* Animations */
@keyframes fadeIn {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}
@keyframes slideIn {
  from {
    transform: translateX(100%);
  }
  to {
    transform: translateX(0);
  }
}
@keyframes slideOut {
  from {
    transform: translateX(0);
  }
  to {
    transform: translateX(-100%);
  }
}
@keyframes fadeSlide {
  from {
    opacity: 0;
    transform: translateY(50%);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}