Enable keyboard control

Former version works with mouse only.
Makes keyboard control available.
Left / Right key for move, Space for game start & shoot.

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Add shot gun and bomb feature

X key for shot gun. It shot 4 bullets concurrently.
Z key for bomb. It explode when hit an enemy.

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Implement bullets control feature

Control bullets's direction/speed using Shift + arrow keys.
It works as powerful as 'torpedo number 1' of North Korea.

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Make arrows and weapons key works simultaneously

Shot while moving was not done. Do it available.

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Implement barrier feature

C key works as barrier.
Barrier exist few seconds and protect user from enemy's bullets.
While barrier is active, user can't shoot any bullet.

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Implement GOD MODE

Enemy shoot lucky bullet by 1/3 random chance.
If user get that bullet, user become GOD.
No limit for attack, No dead for few seconds.

Signed-off-by: SeongJae Park <sj38.park@gmail.com>