Important! Please Read
I have integrated all together for demo, here is what happen in the game
right now:
20 aliens are created after count reach 30000
push button with switch 0 to select and place the space ship
money will be deducted after selected a ship but can go to negative

Here are some bugs and hope to fix before demo (It may be because I do
not have the newest version of alien, bulelts etc)

Bullets do not get clear after shoot.  No explode effect.

Aliens crash the game when reach to earth.

There is still a bit buggy if we select the ship without push in the
middle of button. (Especially button #4)

Other than these, it seems pretty good! Try it out yourself!! :)