html {
  font-family: sans-serif;
}

.container {
  display: flex;
  padding: 10px;
  justify-content: center;
}

.vertical {
  display: flex;
  flex-direction: column;
}

#header {
  display: flex;
  align-items: center;
}

#help-toggle {
  align-self: center;
  border: none;
  background: transparent;
  color: #6c757d;
  margin-left: 5px;
  display: inline;
  cursor: pointer;
}

#help-text {
  align-self: center;
  margin-left: 10px;
  display: inherit;
  max-width: 350px;
}

#config {
  align-items: flex-end;
  justify-content: space-around;
}

#config div {
  padding: 4px;
}

#config label {
  display: inline-block;
}

#config input {
  width: 95%;
}

#problem-set {
  align-items: center;
  text-align: center;
}

#problem-set div, #problem-set pre {
  flex: 1;
  margin: 0 auto;
}

#score, #problem, #timer {
  font-family: monospace;
}

#score {
  font-size: 20px;
}

#problem {
  font-size: 24px;
}

#timer {
  font-size: 16px;
}

#submit, #start {
  border-radius: .25rem;
  padding: .375rem .75rem;
}

button.primary {
  color: #fff;
  background-color: #007bff;
  border-color: #007bff
}

button.primary:hover {
  color: #fff;
  background-color: #0069d9;
  border-color: #0062cc;
}

@keyframes shake {
  10%, 90% {
    transform: translate3d(-1px, 0, 0);
  }

  20%, 80% {
    transform: translate3d(2px, 0, 0);
  }

  30%, 50%, 70% {
    transform: translate3d(-4px, 0, 0);
  }

  40%, 60% {
    transform: translate3d(4px, 0, 0);
  }
}

.apply-shake {
  animation: shake 0.82s cubic-bezier(.36, .07, .19, .97) both;
}

.apply-shake input {
  box-shadow: 0 0 3px #CC0000;
}

@keyframes flash-green {
  0% {
    box-shadow: 0 0 12px #00C000;
  }

  100% {
    box-shadow: none;
  }
}

.correct-answer input {
  animation: flash-green .5s cubic-bezier(0.4, 0, 0.2, 1);
}

.restart-icon {
  align-self: flex-end;
  margin-right: 5px;
}