Omega Factor (Expert Challenge)

Omega Factor is the fourth mission of the first episode in Prismata. Complete all the missions of the episode to unlock the expert mission challenges. This mission is a puzzle that includes economy timing and assigning the optimal amount of damage while defending. Below are hints and a solution.
 *  Victory window message 
 *  This challenge admits a solution in which only a single Engineer is constructed. Can you find it?

Hints and Solution
''Info: Puzzles may have more than one successful strategy and solution. The hints here refer to one solution, described progressively below.

One Engineer
The victory screen hints that the challenge can be cleared without constructing more than one Engineer.

This solution constructs 1 Engineer, 5 Omega Splitters, 0 Steelsplitters, and 23 Walls.