nontrivial — not trivial; requiring significant thought, effort, or consideration; important or complex

a focused engineer examines multiple layered blueprints while pointing at intricate mechanical components. She furrows her brow as she calculates complex measurements and connections between different parts. The detailed schematics show numerous interconnected systems that require careful coordination to work together. Her mistake could cause the entire project to fail, so every decision demands thorough analysis. Her colleague leans in with concern, studying additional technical documents spread across the workbench. Both engineers appear intensely concentrated as they work through each challenging step. a problem that requires significant thought, effort, and consideration to solve properly