:root {
  --primary: #4361ee;
  --secondary: #7209b7;
  --accent: #3a86ff;
  --correct: #4caf50;
  --incorrect: #f44336;
  --light-bg: #f8f9fa;
  --dark-text: #333;
  --light-text: #fff;
  --gray-text: #6c757d;
  --border-radius: 12px;
  --shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
  --transition: all 0.3s ease;
}

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

body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  min-height: 100vh;
  padding: 20px;
  color: var(--dark-text);
  line-height: 1.6;
  overflow-x: hidden;
  position: relative;
}

/* Animované pozadí s duhovými barvami */
.background {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: -2;
  background: linear-gradient(225deg, #ff0000, #ff7700, #ffff00, #00ff00, #0000ff, #8a2be2, #ff00ff);
  background-size: 1400% 1400%;
  animation: rainbowBackground 30s ease infinite;
}

/* Animace pro duhové pozadí */
@keyframes rainbowBackground {
  0% { background-position: 0% 25%; }
  25% { background-position: 50% 50%; }
  50% { background-position: 100% 75%; }
  75% { background-position: 50% 50%; }
  100% { background-position: 0% 25%; }
}

/* Přidání průhlednosti a zeslabení pozadí */
.overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(255, 255, 255, 0.7);
  z-index: -1;
}

/* Bublinky */
.bubble {
  position: fixed;
  border-radius: 50%;
  background: radial-gradient(circle at 30% 30%, rgba(255, 255, 255, 0.8), rgba(255, 255, 255, 0.1));
  box-shadow: 0 0 10px rgba(255, 255, 255, 0.5);
  z-index: -1;
  opacity: 0.6;
  pointer-events: none;
}

header {
  text-align: center;
  margin-bottom: 30px;
  position: relative;
  z-index: 1;
}

h1 {
  font-size: 2.5rem;
  margin-bottom: 10px;
  color: var(--primary);
  text-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

.subtitle {
  font-size: 1.2rem;
  color: var(--gray-text);
  margin-bottom: 20px;
}

.container {
  max-width: 900px;
  margin: 0 auto;
  background: var(--light-text);
  padding: 30px;
  border-radius: var(--border-radius);
  box-shadow: var(--shadow);
  position: relative;
  z-index: 1;
  backdrop-filter: blur(5px);
  background-color: rgba(255, 255, 255, 0.85);
}

.filters {
  display: flex;
  flex-wrap: wrap;
  gap: 15px;
  justify-content: center;
  margin-bottom: 25px;
  padding-bottom: 20px;
  border-bottom: 1px solid rgba(0,0,0,0.1);
}

.filter-group {
  display: flex;
  flex-direction: column;
  min-width: 150px;
}

label {
  font-size: 0.9rem;
  margin-bottom: 5px;
  color: var(--gray-text);
  font-weight: 600;
}

select {
  padding: 12px;
  border-radius: var(--border-radius);
  border: 1px solid #ddd;
  background-color: var(--light-bg);
  font-size: 1rem;
  transition: var(--transition);
  cursor: pointer;
}

select:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(58, 134, 255, 0.2);
}

.btn {
  padding: 12px 24px;
  font-size: 1rem;
  border: none;
  border-radius: var(--border-radius);
  cursor: pointer;
  transition: var(--transition);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
}

.btn-primary {
  background: linear-gradient(to right, var(--primary), var(--secondary));
  color: var(--light-text);
  box-shadow: 0 4px 10px rgba(114, 9, 183, 0.3);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 15px rgba(114, 9, 183, 0.4);
}

.btn-primary:active {
  transform: translateY(1px);
}

.btn-submit {
  margin-top: 15px;
  align-self: center;
}

.exercises-container {
  margin-top: 20px;
}

.exercise {
  background: var(--light-bg);
  border-radius: var(--border-radius);
  margin-bottom: 20px;
  overflow: hidden;
  box-shadow: 0 2px 8px rgba(0,0,0,0.05);
  transition: var(--transition);
  background-color: rgba(255, 255, 255, 0.9);
}

.exercise:hover {
  box-shadow: 0 4px 12px rgba(0,0,0,0.1);
  transform: translateY(-2px);
}

.exercise-header {
  padding: 15px 20px;
  background: linear-gradient(to right, var(--primary), var(--accent));
  color: var(--light-text);
  display: flex;
  justify-content: space-between;
  align-items: center;
  cursor: pointer;
  font-weight: 600;
}

.exercise-title {
  display: flex;
  align-items: center;
  gap: 10px;
}

.exercise-toggle {
  transform: rotate(0deg);
  transition: var(--transition);
}

.exercise-toggle.active {
  transform: rotate(180deg);
}

.exercise-details {
  padding: 0;
  max-height: 0;
  overflow: hidden;
  transition: var(--transition);
}

.exercise-details.active {
  padding: 20px;
  max-height: 800px;
}

.exercise-content {
  margin-bottom: 15px;
}

.exercise-info {
  display: flex;
  flex-wrap: wrap;
  gap: 15px;
  margin-bottom: 15px;
  font-size: 0.9rem;
}

.info-item {
  display: flex;
  align-items: center;
  gap: 5px;
}

.info-item i {
  color: var(--accent);
}

.exercise-description {
  margin-bottom: 20px;
  line-height: 1.7;
}

.btn-start {
  background-color: var(--accent);
  color: var(--light-text);
  padding: 10px 20px;
  border-radius: var(--border-radius);
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-weight: 600;
  box-shadow: 0 3px 8px rgba(58, 134, 255, 0.3);
}

.btn-start:hover {
  background-color: #2a78fc;
  transform: translateY(-2px);
}

.question-container {
  background-color: rgba(67, 97, 238, 0.1);
  border-radius: var(--border-radius);
  padding: 20px;
  margin-top: 20px;
  display: none;
}

.question {
  font-size: 1.1rem;
  margin-bottom: 15px;
  font-weight: 600;
}

.options {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.option {
  padding: 10px 20px;
  border: 2px solid #ddd;
  border-radius: var(--border-radius);
  cursor: pointer;
  transition: var(--transition);
  min-width: 100px;
  text-align: center;
}

.option:hover {
  border-color: var(--accent);
  background-color: rgba(58, 134, 255, 0.1);
}

.option.correct {
  background-color: rgba(76, 175, 80, 0.2);
  border-color: var(--correct);
}

.option.incorrect {
  background-color: rgba(244, 67, 54, 0.2);
  border-color: var(--incorrect);
}

.result-message {
  margin-top: 15px;
  padding: 10px;
  border-radius: var(--border-radius);
  font-weight: 600;
  display: none;
}

.result-message.correct {
  background-color: rgba(76, 175, 80, 0.2);
  color: #2e7d32;
}

.result-message.incorrect {
  background-color: rgba(244, 67, 54, 0.2);
  color: #c62828;
}

.next-btn {
  background-color: var(--primary);
  color: var(--light-text);
  margin-top: 15px;
  display: none;
}

@media (max-width: 768px) {
  .filters {
    flex-direction: column;
    align-items: stretch;
  }

  .filter-group {
    min-width: 100%;
  }

  .exercise-header {
    flex-direction: column;
    align-items: flex-start;
    gap: 10px;
  }

  .exercise-info {
    flex-direction: column;
    gap: 5px;
  }

  .options {
    flex-direction: column;
  }

  .option {
    width: 100%;
  }
}

@media (max-width: 480px) {
  h1 {
    font-size: 2rem;
  }

  .container {
    padding: 20px;
  }
}

/* Styly pro tlačítko "Tvůrci" */
.tvurci-button {
  position: fixed;
  bottom: 20px;
  left: 50%; /* Vycentrování horizontálně */
  transform: translateX(-50%); /* Vycentrování horizontálně */
  background-color: rgba(255, 255, 255, 0.3);
  border: 1px solid rgba(255, 255, 255, 0.5);
  border-radius: 5px;
  padding: 15px 30px; /* Zvětšení paddingu */
  color: white;
  text-decoration: none;
  font-size: 20px; /* Zvětšení písma */
  cursor: pointer;
  z-index: 1000;
  width: auto; /* Automatická šířka podle obsahu */
}

.tvurci-button:hover {
  background-color: rgba(255, 255, 255, 0.5);
}