* {
  box-sizing: border-box;
}

:root {
    /* Color Palette */
    --primary-indigo: #4f46e5;      /* Main brand color (Used for Merge button) */
    --info-blue: #3B82F6;           /* Info card/state */
    --accent-orange: #f97316;       /* Accent color for highlights/active states (Used in Footer/Hover) */
    --danger-red: #dc2626;          /* Danger/Penalty card/state */
    --success-green: #10b981;       /* Success card/state */
    --warning-yellow: #F59E0B;      /* Warning card/state */
    --danger-bg: #FEE2E2;
    
    /* Backgrounds & Text */
    --bg-light: #f9fafb;
    --text-dark: #1f2937;
    
    --footer-bg: #e0e7ff; /* Very light indigo background */
    --footer-text: #4b5563; /* Darker gray text */
    --footer-hover: #1e3a8a; /* Dark blue on hover */
  }

body {
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  background: linear-gradient(180deg, #eef2ff 0%, #f9fafb 50%, #f9fafb 100%); 
  margin: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: flex-start; /* Changed to start for better footer placement */
  align-items: center;
  padding-top: 2rem; /* Adjusted padding */
  color: var(--text-dark);
  overflow-x: hidden;
  line-height: 1.6;
}

.container {
  background: #fff;
  width: 100%;
  max-width: 900px;
  border-radius: 16px; /* Slightly larger radius for softer look */
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.15); /* Stronger shadow */
  padding: 2.5rem 3rem; /* Increased padding */
  margin-bottom: 2rem;
}

/* --- ENHANCED DROPZONE STYLES --- */
#dropzone {
  border: 3px dashed #b8c2ff; /* Lighter dashed line */
  border-radius: 12px;
  padding: 3rem 1rem;
  text-align: center;
  cursor: pointer;
  transition: all 0.3s ease-in-out;
  user-select: none;
  color: var(--primary-indigo); /* Primary color text */
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
  margin-bottom: 1.5rem;
  background: #f0f4ff; /* Light background */
}

#dropzone:hover {
  background-color: #eef2ff;
  border-color: var(--primary-indigo);
  transform: translateY(-2px); /* Subtle lift on hover */
}

#dropzone.dragover {
  background-color: #e3f2fd;
  border-color: var(--info-blue);
  color: var(--info-blue);
  box-shadow: 0 0 10px rgba(79, 70, 229, 0.2);
}

#dropzone svg {
  width: 56px; /* Slightly larger icon */
  height: 56px;
  fill: var(--primary-indigo); /* Primary color icon */
}

#dropzone p {
  margin: 0;
  font-size: 1.2rem;
  font-weight: 600;
}

#fileInput {
  display: none;
}

/* --- FOOTER STYLES (app-footer) --- */
.app-footer { 
    width: 100vw; /* Full viewport width */
    background: var(--footer-bg); 
    color: var(--footer-text); 
    padding: 1.5rem 0; 
    text-align: center; 
    margin-top: auto; 
    display: flex; 
    justify-content: center; 
    align-items: center; 
    flex-direction: column; 
    font-size: 1rem;
    border-top: 5px solid var(--primary-indigo);
    box-shadow: 0 -2px 10px rgba(0, 0, 0, 0.05);
}
.app-footer a { 
    color: var(--primary-indigo); 
    text-decoration: none; 
    font-weight: 600; 
    border-bottom: 1px solid transparent; 
    transition: 0.3s; 
}
.app-footer a:hover { 
    color: var(--footer-hover); 
    border-color: var(--footer-hover); 
}

h1 {
  text-align: center;
  margin-bottom: 1.5rem;
  font-weight: 700;
  color: var(--text-dark);
}

/* === File List Layout === */
#fileListContainer {
  margin-top: 1.5rem;
  max-height: 500px;
  overflow-y: auto;
  padding: 0.5rem;
}

#fileList {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(160px, 1fr)); /* Slightly wider tiles */
  gap: 20px; /* Increased gap */
}

#fileList li {
  position: relative;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: space-between;
  background: #fff;
  border: 1px solid #e5e7eb; /* Thinner, softer border */
  border-radius: 12px;
  padding: 12px;
  cursor: grab;
  height: 230px; /* Increased height */
  box-shadow: 0 4px 10px rgba(0, 0, 0, 0.08); /* Softer shadow */
  transition: transform 0.2s, box-shadow 0.2s, border-color 0.2s;
}

#fileList li:hover {
  border-color: var(--primary-indigo);
  box-shadow: 0 6px 15px rgba(79, 70, 229, 0.2);
}

/* --- Page Count Indicator --- */
.page-count {
  position: absolute;
  bottom: 5px;
  right: 5px;
  background: var(--primary-indigo);
  color: white;
  padding: 2px 8px;
  border-radius: 10px;
  font-size: 0.75rem;
  font-weight: 600;
  z-index: 10;
}

/* === Preview Styles === */
.file-preview {
  width: 100%;
  height: 160px;
  background: #f0f0f0;
  border: 1px solid #ccc;
  flex-shrink: 0;
  position: relative;
  overflow: hidden;
  display: flex;
  justify-content: center;
  align-items: center;
  border-radius: 8px; /* Rounded corners for preview */
  margin-bottom: 10px;
}

/* === File Info === */
.file-name {
  font-size: 0.95rem; /* Slightly larger name */
  font-weight: 600;
}

/* === Drag Handle (Hidden as per previous request) === */
.drag-handle {
  display: none; 
}

/* === Remove Button --- */
.remove-btn {
  position: absolute;
  top: 8px; /* Moved slightly inside */
  right: 8px;
  background: var(--danger-red);
  color: #fff;
  font-size: 0.9rem;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  opacity: 0.8;
  display: flex;
  align-items: center;
  justify-content: center;
}

.remove-btn:hover {
  opacity: 1;
  background-color: #b91c1c;
}

/* --- Sortable Feedback --- */
.sortable-ghost {
  opacity: 0.4;
  background-color: #e0e7ff !important; /* Lighter ghost background */
  border-color: var(--primary-indigo) !important;
  transform: scale(0.98);
}

/* --- ENHANCED MERGE BUTTON --- */
#mergeBtn {
  margin-top: 2rem;
  width: 100%;
  padding: 16px 0; /* Taller button */
  font-size: 1.3rem; /* Larger font */
  font-weight: 700;
  color: #fff;
  background: var(--primary-indigo);
  border: none;
  border-radius: 10px;
  cursor: pointer;
  transition: background-color 0.25s ease, transform 0.1s;
  box-shadow: 0 4px 15px rgba(79, 70, 229, 0.4);
}

#mergeBtn:hover:not(:disabled) {
  background: #4338ca;
  transform: translateY(-1px);
}

#mergeBtn:disabled {
  background: #a5b4fc; /* Lighter primary-indigo shade */
  cursor: not-allowed;
  box-shadow: none;
}