@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap');

:root {
  --primary-color: #2563eb;
  --secondary-color: #3b82f6;
  --accent-color: #60a5fa;
  --background-color: #ffffff;
  --text-color: #1f2937;
  --border-color: #e5e7eb;
  --success-color: #10b981;
  --error-color: #ef4444;
}

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

body {
  font-family: 'Inter', sans-serif;
  background-color: var(--background-color);
  color: var(--text-color);
  line-height: 1.6;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 1rem;
}

/* Header Styles */
header {
  background-color: var(--background-color);
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
  position: fixed;
  width: 100%;
  top: 0;
  z-index: 1000;
}

header nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem 0;
}

.logo {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--primary-color);
  text-decoration: none;
  transition: color 0.3s ease;
}

.logo:hover {
  color: var(--secondary-color);
}

.nav-links {
  display: flex;
  gap: 1.5rem;
  align-items: center;
}

.nav-link {
  color: var(--text-color);
  text-decoration: none;
  font-weight: 500;
  transition: color 0.3s ease;
}

.nav-link:hover {
  color: var(--primary-color);
}

/* Challenge Grid */
.challenge-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1.5rem;
  padding: 2rem 0;
  margin-top: 4rem;
}

/* Challenge Card */
.challenge-card {
  background: var(--background-color);
  border-radius: 12px;
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
  padding: 1.5rem;
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.challenge-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 8px 12px rgba(0, 0, 0, 0.15);
}

.challenge-card h3 {
  font-size: 1.5rem;
  margin-bottom: 1rem;
  color: var(--text-color);
}

.difficulty {
  display: inline-block;
  padding: 0.25rem 0.75rem;
  border-radius: 9999px;
  font-size: 0.875rem;
  font-weight: 500;
  margin-bottom: 1rem;
}

.difficulty.easy { background-color: var(--success-color); color: white; }
.difficulty.medium { background-color: #f59e0b; color: white; }
.difficulty.hard { background-color: var(--error-color); color: white; }

/* Form Elements */
.answer-form {
  margin-top: 1rem;
}

.answer-form input[type="text"] {
  width: 100%;
  padding: 0.75rem 1rem;
  border: 2px solid var(--border-color);
  border-radius: 6px;
  font-family: 'Inter', sans-serif;
  font-size: 1rem;
  transition: border-color 0.3s ease;
}

.answer-form input[type="text"]:focus {
  outline: none;
  border-color: var(--primary-color);
}

.answer-form button {
  width: 100%;
  padding: 0.75rem 1rem;
  margin-top: 0.5rem;
  background-color: var(--primary-color);
  color: white;
  border: none;
  border-radius: 6px;
  font-family: 'Inter', sans-serif;
  font-size: 1rem;
  font-weight: 500;
  cursor: pointer;
  transition: background-color 0.3s ease;
}

.answer-form button:hover {
  background-color: var(--secondary-color);
}

/* Animations */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}

.animate-fade-in {
  animation: fadeIn 0.5s ease forwards;
}

/* Success/Error Messages */
.message {
  padding: 1rem;
  border-radius: 6px;
  margin: 1rem 0;
}

.message.success {
  background-color: rgba(16, 185, 129, 0.1);
  border: 1px solid var(--success-color);
  color: var(--success-color);
}

.message.error {
  background-color: rgba(239, 68, 68, 0.1);
  border: 1px solid var(--error-color);
  color: var(--error-color);
}

/* Hero Section */
.hero-section {
  text-align: center;
  padding: 6rem 0 4rem;
  margin-bottom: 2rem;
}

.hero-section h1 {
  font-size: 3rem;
  color: var(--text-color);
  margin-bottom: 1rem;
}

.hero-section p {
  font-size: 1.25rem;
  color: var(--text-color);
  opacity: 0.8;
  max-width: 600px;
  margin: 0 auto;
}

/* Challenge Container */
.challenge-container {
  padding: 2rem;
  background: white;
  border-radius: 12px;
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
  margin-top: 5rem;
}

.challenge-header {
  margin-bottom: 2rem;
}

.challenge-meta {
  display: flex;
  gap: 1rem;
  margin-top: 1rem;
  font-size: 0.875rem;
}

.challenge-content {
  margin-bottom: 2rem;
}

/* Hints Section */
.hints-section {
  margin-top: 2rem;
  padding-top: 2rem;
  border-top: 1px solid var(--border-color);
}

.hints-container {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  margin-top: 1rem;
}

.hint-toggle {
  background: none;
  border: 2px solid var(--primary-color);
  color: var(--primary-color);
  padding: 0.5rem 1rem;
  border-radius: 6px;
  cursor: pointer;
  font-family: 'Inter', sans-serif;
  font-weight: 500;
  transition: all 0.3s ease;
}

.hint-toggle:hover {
  background: var(--primary-color);
  color: white;
}

.hint-content {
  margin-top: 1rem;
  padding: 1rem;
  background: rgba(37, 99, 235, 0.1);
  border-radius: 6px;
  font-size: 0.875rem;
}

/* Filters */
.filters {
  margin: 2rem 0;
}

.filter-group {
  display: flex;
  align-items: center;
  gap: 1rem;
  flex-wrap: wrap;
}

.filter-btn {
  padding: 0.5rem 1rem;
  border: 2px solid var(--primary-color);
  border-radius: 6px;
  background: none;
  color: var(--primary-color);
  cursor: pointer;
  font-family: 'Inter', sans-serif;
  font-weight: 500;
  transition: all 0.3s ease;
}

.filter-btn:hover,
.filter-btn.active {
  background: var(--primary-color);
  color: white;
}

/* Responsive Design */
@media (max-width: 768px) {
  .challenge-grid {
    grid-template-columns: 1fr;
  }
  
  .container {
    padding: 0 1.5rem;
  }
  
  .hero-section {
    padding: 4rem 0 2rem;
  }
  
  .hero-section h1 {
    font-size: 2.5rem;
  }
}