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/ShipDeckScene.js

@@ -76,16 +76,21 @@ export default class ShipDeckScene extends Phaser.Scene {
             this.showMessage(`Whale oil: ${this.inventory.whaleOil} barrels. Your precious cargo!`);
         });
 
-        // Penguin cage (dark humor ahead)
-        const penguinCage = this.add.rectangle(650, 350, 80, 80, 0x333333);
-        penguinCage.setInteractive({ useHandCursor: true });
-        penguinCage.setStrokeStyle(3, 0x000000);
+        // Penguin cage (hidden until discovered)
+        this.penguinCage = this.add.rectangle(650, 350, 80, 80, 0x333333);
+        this.penguinCage.setInteractive({ useHandCursor: true });
+        this.penguinCage.setStrokeStyle(3, 0x000000);
 
-        this.add.text(650, 350, '🐧', {
+        this.penguinEmoji = this.add.text(650, 350, '🐧', {
             fontSize: '32px'
         }).setOrigin(0.5);
 
-        penguinCage.on('pointerdown', () => {
+        // Hide penguin elements if not yet discovered
+        const discovered = this.inventory.penguins > 0;
+        this.penguinCage.setVisible(discovered);
+        this.penguinEmoji.setVisible(discovered);
+
+        this.penguinCage.on('pointerdown', () => {
             if (this.inventory.penguins > 0) {
                 this.showMessage(`${this.inventory.penguins} penguins. They're... emergency fuel. Dark times call for dark measures.`);
             } else {
@@ -130,12 +135,25 @@ export default class ShipDeckScene 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)
+        const discovered = this.inventory.penguins > 0;
+        if (discovered) {
+            lines.push(`Penguins: ${this.inventory.penguins}/20`);
+        }
+
+        this.inventoryText.setText(lines);
+
+        // Update penguin cage visibility
+        if (this.penguinCage) {
+            this.penguinCage.setVisible(discovered);
+            this.penguinEmoji.setVisible(discovered);
+        }
     }
 
     createMessageBox() {