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

body {
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
}

.presentation-container {
  width: 90vw;
  height: calc(90vw * 9 / 16);
  max-width: 1200px;
  max-height: 675px;
  position: relative;
  display: flex;
  flex-direction: column;
  justify-content: center;
}

/* Ensure 16:9 aspect ratio is maintained even on tall screens */
@media (max-height: calc(90vw * 9 / 16 + 100px)) {
  .presentation-container {
    height: 90vh;
    width: calc(90vh * 16 / 9);
  }
}

.slide {
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  border-radius: 20px;
  padding: 50px 60px;
  text-align: center;
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
  display: none;
  flex: 1;
  flex-direction: column;
  justify-content: center;
  transition: all 0.4s ease;
  cursor: pointer;
  position: absolute;
  width: 100%;
  height: 100%;
  box-sizing: border-box;
  opacity: 0;
  transform: translateX(50px);
}

.slide.active {
  display: flex;
  opacity: 1;
  transform: translateX(0);
}

.slide h1 {
  font-size: 3.2em;
  color: #2c3e50;
  margin-bottom: 25px;
  font-weight: 700;
}

.slide h2 {
  font-size: 2.8em;
  color: #34495e;
  margin-bottom: 35px;
  font-weight: 600;
}

.slide p {
  font-size: 1.5em;
  color: #555;
  line-height: 1.6;
  max-width: 800px;
  margin: 0 auto;
}

.slide .highlight {
  color: #8e44ad;
  font-weight: 600;
}

.slide img {
  max-width: 100%;
  height: auto;
  object-fit: contain;
}

.navigation {
  position: fixed;
  bottom: 30px;
  left: 50%;
  transform: translateX(-50%);
  display: flex;
  gap: 15px;
  align-items: center;
  z-index: 1000;
}

.nav-btn {
  background: rgba(255, 255, 255, 0.9);
  border: none;
  padding: 12px 24px;
  border-radius: 25px;
  cursor: pointer;
  font-size: 16px;
  font-weight: 600;
  color: #667eea;
  transition: all 0.3s ease;
  box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
}

.nav-btn:hover {
  background: white;
  transform: translateY(-2px);
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.15);
}

.nav-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.slide-counter {
  background: rgba(255, 255, 255, 0.9);
  padding: 8px 16px;
  border-radius: 20px;
  font-weight: 600;
  color: #667eea;
}

.slide-indicator {
  position: fixed;
  top: 30px;
  right: 30px;
  background: rgba(142, 68, 173, 0.1);
  padding: 10px 20px;
  border-radius: 15px;
  font-weight: 600;
  color: #8e44ad;
  z-index: 1000;
  backdrop-filter: blur(10px);
}

@media (max-width: 768px) {
  .presentation-container {
    width: 95vw;
    height: calc(95vw * 9 / 16);
    max-height: 85vh;
  }

  /* On mobile, prioritize height if needed */
  @media (max-height: calc(95vw * 9 / 16 + 80px)) {
    .presentation-container {
      height: 85vh;
      width: calc(85vh * 16 / 9);
    }
  }

  .slide {
    padding: 25px 15px;
    border-radius: 15px;
  }

  .slide h1 {
    font-size: 2em;
  }

  .slide h2 {
    font-size: 1.6em;
  }

  .slide p {
    font-size: 1.1em;
  }

  .slide img {
    max-height: 250px;
  }

  .navigation {
    bottom: 15px;
  }

  .slide-indicator {
    top: 15px;
    right: 15px;
    padding: 6px 12px;
    font-size: 0.9em;
  }
}