Hide penguin references until feature is discovered

- Penguin inventory line only shows when penguins > 0
- Penguin cage and emoji on ship deck hidden until discovered
- Antarctic Island description made mysterious (no penguin mention)
- Penguin cage visibility updates when inventory changes
- Creates surprise discovery moment when visiting Antarctic Island
- Maintains dark humor reveal during gameplay

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/scenes/MapScene.js

@@ -34,9 +34,9 @@ export default class MapScene extends Phaser.Scene {
             'Rich waters where whales gather. Dangerous but profitable!',
             () => this.goToHunting());
 
-        // Antarctic Island (for penguins)
+        // Antarctic Island
         this.createLocation(600, 450, 'ANTARCTIC\nISLAND', 0xE0E0E0,
-            'Cold, desolate islands inhabited by penguins...',
+            'Cold, desolate islands. Who knows what resources might be found...',
             () => this.goToAntarctic());
 
         // Port
@@ -126,12 +126,18 @@ export default class MapScene extends Phaser.Scene {
     }
 
     updateInventoryDisplay() {
-        this.inventoryText.setText([
+        const lines = [
             'Inventory:',
             `Fuel: ${this.inventory.fuel}/100`,
-            `Oil: ${this.inventory.whaleOil}/50`,
-            `Penguins: ${this.inventory.penguins}/20`
-        ]);
+            `Oil: ${this.inventory.whaleOil}/50`
+        ];
+
+        // Only show penguins if discovered (have at least one)
+        if (this.inventory.penguins > 0) {
+            lines.push(`Penguins: ${this.inventory.penguins}/20`);
+        }
+
+        this.inventoryText.setText(lines);
     }
 
     createMessageBox() {