Issues fixed added futher enhancements as well

[vashishtpurani]

Changes Made

1. Difficulty Selection

   • Added a pre-game menu to select difficulty (Easy / Medium / Hard) affecting initial game speed.

2. Dynamic Difficulty

   • Game speed increases progressively as the snake eats food (speed decreases by 20ms per food, min 80ms).

3. Score Tracking

   • Introduced score variable, updated by +10 per food eaten.
   • Score displayed continuously, and final score shown on game over.

4. Poisonous Food

   • Added poison food (🍄) that ends the game if eaten.
   • Poison spawns randomly, never inside the snake, and never on the same cell as normal food.
   • Poison repositions each time normal food is consumed.

5. Safe Food/Poison Generation

   • Refactored food generation to ensure food and poison do not overlap or appear inside the snake.

6. Game Rendering Updates

   • Displayed current speed, score, and snake length continuously during gameplay.