Finish polishing

See merge request !19

Update: Game class, Enemy class, let game handle enemy missiles so the don't despawn when the enemy is destroyed

Finish Feature: Console_Start_Menu

See merge request !17

Feature: Console start menu

See merge request !16

Finish Feature: Audio

See merge request !15

Finish Feature: Scoring_System

See merge request !13

Feature: Scoring system

See merge request !12

Update: Game class, now asks the player to enter their name at the end of a game, to save their highscore

Score is increased when an enemy is hit.
When the game ends the final score is displayed.

Update: Ship class, Game class, when ship gets hit by a bullet it loses a life, it's position is reset and it becomes invincible for a short time.
When all lives are depleted the console prints "End Game".

Finish Collision_Detection

See merge request !11

Feature: Collision detection

See merge request !10

Update: Ship class, Enemy class, remove active missile limitation, since missiles now get destroyed when they leave the screen.