:root {
  --text: #1f2937;
  --card: rgba(255,255,255,0.75);
  --border: rgba(0,0,0,0.15);
}

body.dark {
  --text: #f8fafc;
  --card: rgba(30,41,59,0.8);
  --border: rgba(255,255,255,0.2);
}

/* RESET */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: system-ui, sans-serif;
}

/* 🌈 ANIMATED GRADIENT BACKGROUND (OPTION 1) */
body {
  min-height: 100vh;
  color: var(--text);
  background: linear-gradient(
    -45deg,
    #6366f1,
    #8b5cf6,
    #06b6d4,
    #22c55e
  );
  background-size: 400% 400%;
  animation: gradientMove 15s ease infinite;
}

/* Background animation */
@keyframes gradientMove {
  0% { background-position: 0% 50%; }
  50% { background-position: 100% 50%; }
  100% { background-position: 0% 50%; }
}

/* GRID LAYOUT */
.app {
  display: grid;
  grid-template-areas:
    "header header"
    "sidebar main"
    "footer footer";
  grid-template-columns: 240px 1fr;
  grid-template-rows: auto 1fr auto;
  min-height: 100vh;
  backdrop-filter: blur(4px);
}

/* HEADER */
.header {
  grid-area: header;
  position: sticky;
  top: 0;
  z-index: 10;
  background: var(--card);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border);
  padding: 1rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.controls button {
  margin-left: 0.5rem;
  cursor: pointer;
}

/* SIDEBAR */
.sidebar {
  grid-area: sidebar;
  background: var(--card);
  backdrop-filter: blur(14px);
  padding: 1rem;
  border-right: 1px solid var(--border);
  transition: transform 0.3s ease;
}

.sidebar nav a {
  display: block;
  padding: 0.9rem;
  margin-bottom: 0.5rem;
  text-decoration: none;
  color: var(--text);
  border-radius: 8px;
}

.sidebar nav a:hover {
  background: rgba(0,0,0,0.08);
}

/* MAIN */
.main {
  grid-area: main;
  padding: 1rem;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1rem;
}

/* CARD */
.card {
  background: var(--card);
  backdrop-filter: blur(18px);
  border-radius: 16px;
  padding: 1.5rem;
  display: flex;
  justify-content: space-between;
  font-size: 1.2rem;
  cursor: grab;
  border: 1px solid var(--border);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
  animation: fadeIn 0.6s ease;
}

.card:hover {
  transform: translateY(-6px) scale(1.03);
  box-shadow: 0 20px 40px rgba(0,0,0,0.25);
}

.card.active {
  grid-column: span 2;
  font-size: 1.5rem;
}

/* FOOTER */
.footer {
  grid-area: footer;
  text-align: center;
  padding: 0.8rem;
  background: var(--card);
  backdrop-filter: blur(14px);
  border-top: 1px solid var(--border);
}

/* GRID INSPECT MODE */
.inspect .main {
  background-image:
    linear-gradient(to right, rgba(0,0,0,0.15) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(0,0,0,0.15) 1px, transparent 1px);
  background-size: 80px 80px;
}

/* ALT LAYOUT */
.alt-layout .main {
  grid-template-columns: repeat(2, 1fr);
}

/* FADE ANIMATION */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

/* RESPONSIVE */
@media (max-width: 768px) {
  .app {
    grid-template-areas:
      "header"
      "main"
      "footer";
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: fixed;
    height: 100%;
    transform: translateX(-100%);
  }

  .sidebar.active {
    transform: translateX(0);
  }
}