# Health UI Display Fix

## Problem
The health UI was not displaying when the player took damage. The HUD needs to show above the inventory with proper z-index layering.

## Solution

### Changes Made

#### 1. Updated `js/ui/health-ui.js`
- **Changed from emoji hearts to PNG image icons**
  - Full heart: `assets/icons/heart.png`
  - Half heart: `assets/icons/heart-half.png`
  - Empty heart: `assets/icons/heart.png` with 20% opacity

- **Updated HTML structure**
  - Changed from `<div>` with text content to `<img>` elements
  - Container now uses `id="health-ui-container"` (outer wrapper)
  - Inner display uses `id="health-ui"` with `class="health-ui-display"`
  - Each heart is an `<img>` with `class="health-heart"`

- **Updated display method**
  - Changed from `display: 'block'` to `display: 'flex'` for proper alignment
  - Removed inline styles - moved all styling to CSS file

#### 2. Created `css/health-ui.css`
New CSS file with proper styling:

```css
#health-ui-container {
  position: fixed;
  top: 60px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 1100;              /* ABOVE inventory (z-index: 1000) */
  pointer-events: none;       /* Don't block clicks */
}

.health-ui-display {
  display: flex;
  gap: 8px;
  align-items: center;
  justify-content: center;
  padding: 12px 16px;
  background: rgba(0, 0, 0, 0.8);
  border: 2px solid #333;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.9), inset 0 0 5px rgba(0, 0, 0, 0.5);
}

.health-heart {
  width: 32px;
  height: 32px;
  image-rendering: pixelated;  /* Maintain pixel-art style */
  image-rendering: -moz-crisp-edges;
  image-rendering: crisp-edges;
  transition: opacity 0.2s ease-in-out;
  display: block;
}

.health-heart:hover {
  filter: drop-shadow(0 0 4px rgba(255, 0, 0, 0.6));
}
```

#### 3. Updated `index.html`
- Added `<link rel="stylesheet" href="css/health-ui.css">` after inventory.css

## Key Features

### Z-Index Stack
```
z-index: 2000 - Minigames (laptop popup, etc.)
z-index: 1100 - Health UI ✅ (NOW VISIBLE ABOVE INVENTORY)
z-index: 1000 - Inventory UI
z-index: 100  - Legacy elements
```

### Heart Display Logic
- **Full Heart (100%)**: `assets/icons/heart.png` at opacity 1.0
- **Half Heart (50%)**: `assets/icons/heart-half.png` at opacity 1.0
- **Empty Heart (0%)**: `assets/icons/heart.png` at opacity 0.2

### Visibility Rules
- **Hidden**: When at full health (hp === maxHP)
- **Shown**: When damaged (hp < maxHP) OR when KO'd (PLAYER_KO event)
- **Updated**: Every time PLAYER_HP_CHANGED event fires

### Styling
- Dark semi-transparent background: `rgba(0, 0, 0, 0.8)`
- 2px dark border for pixel-art style consistency
- Box shadow for depth (outer + inner)
- Hover effect with red glow on hearts
- Pixelated image rendering for crisp appearance at any scale

## Visual Location

```
┌─────────────────────────────────────┐
│  ❤️ ❤️ ❤️ ❤️ 💔  ← Health UI (NEW)  │
│  (Top center, above inventory)      │
│                                     │
│  [Main Game Area]                   │
│                                     │
│  [Inventory on right side] ← Below  │
│  - Item 1                           │
│  - Item 2                           │
│  - Item 3                           │
└─────────────────────────────────────┘
```

## Testing

1. **Load the game** in `index.html`
2. **Trigger damage** (fight hostile NPC or take damage)
3. **Verify display**:
   - Health UI appears at top center
   - Positioned above inventory
   - Uses PNG heart icons
   - Shows correct number of full/half/empty hearts
   - Updates when HP changes
   - Hides when back to full health

### Expected Console Output
```
✅ Health UI initialized
```

### Expected Heart Display States

| HP | Out of 100 | Display |
|----|----|---------|
| 100 | 5/5 | ❤️ ❤️ ❤️ ❤️ ❤️ (not visible - hidden) |
| 80 | 4/5 | ❤️ ❤️ ❤️ ❤️ 🖤 |
| 60 | 3/5 | ❤️ ❤️ ❤️ 🖤 🖤 |
| 50 | 2.5/5 | ❤️ ❤️ 💔 🖤 🖤 |
| 40 | 2/5 | ❤️ ❤️ 🖤 🖤 🖤 |
| 20 | 1/5 | ❤️ 🖤 🖤 🖤 🖤 |
| 10 | 0.5/5 | 💔 🖤 🖤 🖤 🖤 |
| 0 | 0/5 | 🖤 🖤 🖤 🖤 🖤 |

## Files Modified

1. **js/ui/health-ui.js** - Updated to use PNG icons, removed inline styles
2. **css/health-ui.css** - NEW file with proper styling and z-index
3. **index.html** - Added health-ui.css link

## Asset Files Used

- `assets/icons/heart.png` - Full/empty heart
- `assets/icons/heart-half.png` - Half heart (for remainder health)

Both files already exist in the project.

## Event Integration

The health UI automatically responds to:
- `CombatEvents.PLAYER_HP_CHANGED` - Updates heart display
- `CombatEvents.PLAYER_KO` - Shows UI when player is defeated

These events are emitted by the combat system when health changes.

## Browser Compatibility

- ✅ Firefox (image-rendering: -moz-crisp-edges)
- ✅ Chrome/Edge (image-rendering: crisp-edges)
- ✅ Safari (image-rendering: pixelated)
- ✅ All modern browsers supporting CSS3

## Troubleshooting

| Issue | Cause | Fix |
|-------|-------|-----|
| Health UI not visible | CSS not loaded | Check health-ui.css link in index.html |
| Icons blurry | Rendering mode wrong | Check image-rendering in CSS |
| Behind inventory | Z-index too low | Should be 1100 (above inventory's 1000) |
| Hearts all full | No damage event | Verify PLAYER_HP_CHANGED event fires |
| Emoji showing | Old code running | Hard refresh (Ctrl+Shift+R) |

## Performance

- **Minimal DOM**: Only 5 img elements + 1 container
- **No animations**: Uses opacity transitions only (GPU-accelerated)
- **Lazy rendering**: Only updates when health changes
- **Pointer-events: none**: Doesn't interfere with game input
