```css
/* css/style.css */

:root {
  --color-bg: #0f172a;
  --color-card: #1e293b;
  --color-primary: #8b5cf6;
  --color-secondary: #f43f5e;
  --color-text: #f8fafc;
  --color-muted: #94a3b8;
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);
}

/* Core Styles */
body {
  font-family: system-ui, -apple-system, sans-serif;
  background-color: var(--color-bg);
  color: var(--color-text);
  line-height: 1.5;
}

header {
  margin-bottom: 2rem;
  padding: 1rem 0;
  display: flex;
  justify-content: flex-start;
  }

header img {
  height: 6rem;
  width: auto;
  max-width: none;
  }
   
   .container {
    max-width: 1480px;
    margin: 0 auto;
    padding: 1rem;
   }

/* Video Grid */
#videoList {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 2rem;
  padding: 1.5rem 0;
}

/* Video Cards */
.video-card {
  background-color: var(--color-card);
  border-radius: 0.75rem;
  overflow: hidden;
  transition: transform 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  box-shadow: var(--shadow-md);
}

.video-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.video-card .thumbnail-container {
  position: relative;
  padding-top: 56.25%;
  background-color: #0f172a;
}

.video-card img.thumbnail {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.video-card .details {
  padding: 1.25rem;
}

.video-card h3 {
  font-size: 1.125rem;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: 0.75rem;
}

/* Modal Player */
#playerModal {
  position: fixed;
  inset: 0;
  background-color: rgb(0 0 0 / 0.8);
  backdrop-filter: blur(8px);
  z-index: 50;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1.5rem;
}

.modal-content {
  background-color: var(--color-card);
  border-radius: 1rem;
  width: 100%;
  max-width: 64rem;
  max-height: 90vh;
  overflow-y: auto;
  box-shadow: var(--shadow-lg);
}

/* Progress Bars */
.progress-bar {
  width: 100%;
  height: 0.5rem;
  background-color: rgb(255 255 255 / 0.1);
  border-radius: 9999px;
  overflow: hidden;
}

.progress-bar-fill {
  height: 100%;
  background-color: var(--color-primary);
  transition: width 0.3s ease-out;
}

/* Forms & Inputs */
input, textarea {
  width: 100%;
  padding: 0.75rem;
  background-color: var(--color-bg);
  border: 1px solid rgb(255 255 255 / 0.1);
  border-radius: 0.5rem;
  color: var(--color-text);
  transition: border-color 0.2s;
}

input:focus, textarea:focus {
  outline: none;
  border-color: var(--color-primary);
  ring: 2px var(--color-primary);
}

/* Buttons */
button {
  padding: 0.75rem 1.5rem;
  background-color: var(--color-primary);
  color: white;
  border-radius: 0.5rem;
  font-weight: 500;
  transition: all 0.2s;
}

button:hover {
  background-color: var(--color-secondary);
  transform: translateY(-1px);
}

button:focus {
  outline: none;
  ring: 2px var(--color-primary);
}

/* Utility Classes */
.line-clamp-2 {
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.hidden {
  display: none;
}

/* Notifications */
#errorContainer, #successContainer {
  border-radius: 0.5rem;
  padding: 1rem;
  margin-bottom: 1rem;
  display: flex;
  align-items: center;
}

#errorContainer {
  background-color: rgb(220 38 38 / 0.1);
  color: #fecaca;
  border: 1px solid rgb(220 38 38 / 0.2);
}

#successContainer {
  background-color: rgb(34 197 94 / 0.1);
  color: #bbf7d0;
  border: 1px solid rgb(34 197 94 / 0.2);
}

/* Modal Display */
#playerSection, #playerModal {
  display: none;
}

#playerModal.flex {
  display: flex;
}

/* Responsive Design */
@media (max-width: 640px) {
  #videoList {
    grid-template-columns: 1fr;
    gap: 1rem;
  }
  
  .container {
    padding: 0.75rem;
  }
}

footer {
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  margin-top: 4rem;
  padding-top: 2rem;
}

footer a {
  text-decoration: none;
}

footer a:hover {
  text-decoration: underline;
}
```