:root{
  --navy:#0A3161;
  --red:#B31942;
  --white:#FFFFFF;
  --dark:#081b35;
  --light:#f2f4f8;
}

*{
  margin:0;
  padding:0;
  box-sizing:border-box;
}

body{
  font-family:Arial, Helvetica, sans-serif;
  background:linear-gradient(180deg,var(--navy),#041225);
  color:var(--white);
  min-height:100vh;
}

.app{
  width:100%;
  min-height:100vh;
  display:flex;
  justify-content:center;
  align-items:center;
  padding:20px;
}

.screen{
  display:none;
  width:100%;
  max-width:500px;
}

.screen.active{
  display:block;
}

.card{
  background:rgba(255,255,255,0.08);
  backdrop-filter:blur(8px);
  border:2px solid rgba(255,255,255,0.1);
  border-radius:24px;
  padding:32px 24px;
  text-align:center;
  box-shadow:0 12px 30px rgba(0,0,0,0.35);
}

h1{
  font-size:2rem;
  line-height:1.2;
  margin-bottom:12px;
}

.subtitle{
  color:#d9e4ff;
  margin-bottom:24px;
}

.flag-line{
  height:6px;
  background:linear-gradient(
    90deg,
    var(--red) 0%,
    var(--white) 50%,
    var(--navy) 100%
  );
  border-radius:999px;
  margin-bottom:24px;
}

.instructions{
  list-style:none;
  text-align:left;
  margin-bottom:32px;
}

.instructions li{
  padding:12px 0;
  border-bottom:1px solid rgba(255,255,255,0.1);
}

.primary-btn,
.secondary-btn{
  width:100%;
  border:none;
  border-radius:16px;
  padding:18px;
  font-size:1rem;
  font-weight:bold;
  cursor:pointer;
  transition:0.2s ease;
}

.primary-btn{
  background:var(--red);
  color:var(--white);
}

.primary-btn:hover{
  transform:scale(1.02);
}

.secondary-btn{
  background:var(--white);
  color:var(--navy);
}

.top-bar{
  text-align:center;
  margin-bottom:20px;
  font-weight:bold;
  letter-spacing:1px;
}

.workout-container{
  text-align:center;
}

.exercise-name{
  font-size:2rem;
  font-weight:bold;
  margin-bottom:30px;
}

.timer{
  font-size:7rem;
  font-weight:bold;
  line-height:1;
  margin-bottom:20px;
}

.warning{
  color:#ffb3b3;
  font-size:1.2rem;
  margin-bottom:20px;
  animation:flash 1s infinite;
}

.hidden{
  visibility:hidden;
}

.progress-wrapper{
  width:100%;
  height:16px;
  background:rgba(255,255,255,0.15);
  border-radius:999px;
  overflow:hidden;
  margin:24px 0;
}

.progress-bar{
  height:100%;
  width:100%;
  background:linear-gradient(90deg,var(--red),var(--white),var(--navy));
  transition:width 1s linear;
}

.finish-text{
  margin:20px 0 30px;
  font-size:1.2rem;
}

.button-group{
  display:flex;
  flex-direction:column;
  gap:16px;
}

@keyframes flash{
  0%{opacity:1;}
  50%{opacity:0.2;}
  100%{opacity:1;}
}

@media(min-width:768px){
  .timer{
    font-size:9rem;
  }

  h1{
    font-size:2.5rem;
  }
}