Bonus options:
Complete the game under the "Regular" difficulty setting to access level 
select and enemy ship preview options. 

Alternate mode selection screen:
Complete the game under the "Beginner" difficulty setting to change the 
background on the mode selection screen. 

Avoid damage:
Roll if your ship is about to be hit by a missile. If done correctly, the 
missile will bounce off your ship. 

Extra areas:
Perform the following tasks to reach extra areas in the game. 

Mission 1
Locate the four blue towers surrounding a red tower before the level turns 90 
degree upwards. Destroy the four blue towers, then destroy the red tower. 
Another path with a new Boss, bonus area, and 10 million points will become 
available. 

Mission 3
Locate the area with six green and one red ship. Destroy the red ship without 
hitting any of the green ships. 

Mission 4
Locate the area with four green and four red ships. Wait until the red ships 
fly over the triangular blocks. Then, shoot them as they are going to exit 
from the top of the screen.