Gameplay
The player must progress through 16 different levels, defeating the boss at the end of each level. The player controls their ship using an 8-way joystick and 2 buttons (one button targets enemies in the air, and the other targets the enemies on the ground). The power of the player's ship increases as it evolves.
There are two broad categories that define how enemies attack. The first type only shoots in the forward direction at a constant speed, but the second type shoots bullets that travel at different speeds depending on its distance with the player's ship (the bullets travel quicker if the player is farther away, and slower if the player is close by). This made it so that staying away from enemies would not necessarily make it easier to avoid attacks. The game's difficulty also does not change overtime, and enemies do not become stronger as the player's ship evolves. This style was continued in the game's sequel.
Once the player reaches 2,000,000 points, they gain a bonus of 2,000,000 points, and a bonus of 3,000,000 points once they reach 3,000,000 points. This bonus system allows the player to reach 10,000,000 points after gaining only 5,000,000 points, but the game's counter does not display digits in the ten millions. Destroying 16 ground enemies in a row in the desert level extends gameplay without having to insert additional credits.
Read more about this topic: Darwin 4078