/* Copyright John Salguero All rights Reserved */
html, body {
  margin: 0;
  height: 100vh;
  overflow: hidden;

  background: linear-gradient(-45deg, #0f172a, #1e293b, #0ea5e9, #22c55e);
  background-size: 400% 400%;
  animation: gradientShift 12s ease infinite;

  color: white;
  font-family: Arial;
}

#timer {
  position: absolute;
  top: 20px;
  right: 20px;
  width: 60px;
  height: 60px;
  z-index: 10;
}

#timer svg {
  transform: rotate(-90deg); /* start from top */
}

#timer-bg {
  fill: none;
  stroke: rgba(255,255,255,0.2);
  stroke-width: 8;
}

#timer-progress {
  fill: none;
  stroke: #22c55e; /* green */
  stroke-width: 8;
  stroke-linecap: round;
  transition: stroke-dashoffset 1s linear;
}

#timer-text {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  font-size: 28px;
  font-weight: bold;
  color: white;
}

#problem {
  position: absolute;
  top: 15%;
  left: 50%;
  transform: translateX(-50%);

  font-size: 76px;
  text-align: center;
}

#equation-main, #equation-next {
  position: absolute;
  top: 30%;
  left: 50%;
  transform: translateX(-50%);
  font-size: 48px;
  transition: all 0.5s ease;
}

#equation-next {
  opacity: 0;
  transform: translate(-50%, 40px); /* start slightly below */
}

#explanation {
  position: absolute;
  top: 45%;
  left: 50%;
  transform: translateX(-50%);
  font-size: 24px;
  opacity: 0.8;
}

#steps {
  position: absolute;
  top: 27%;                 /* below the problem */
  left: 50%;
  transform: translateX(-50%);

  width: 800px;
  text-align: center;
  font-size: 28px;
}

#waveCanvas {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 0;
}

#particleCanvas {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 0;
}

#timer.low {
  animation: pulse 1s infinite;
}

.fade-out {
  opacity: 0;
  transform: translateX(-50%) scale(0.95);
}

.fade-in {
  opacity: 1;
  transform: translateX(-50%) scale(1);
}

.move-up {
  transform: translate(-50%, 0);
}

@keyframes pulse {
  0% { transform: scale(1); }
  50% { transform: scale(1.1); }
  100% { transform: scale(1); }
}

@keyframes gradientShift {
  0% { background-position: 0% 50%; }
  50% { background-position: 100% 50%; }
  100% { background-position: 0% 50%; }
}