I have come up with an map design for the level.

I have set it up so that each area is like an arena that the player must complete certain objectives to move on to the next. Once complete the player can move to the next area through the long path which is to represent a path to glory.

In the first area the player needs to survive the onslaught of enemies before the next area opens up.
Area 2 they will need to collect items to assemble the weapon while enemies are attacking.
The next area is another survival while the weapon is being put together.
Then they go and kill 150 enemies with the new weapon.
finally the need to disable the enemy ships by destroying their weak spots.