A hard test for a hard game genre.

Prompt

I am building a 2D isometric modern warfare RTS game. I need you to design and implement the core system for Line of Sight (LOS) and Directional Cover (Defilade). Please write the foundational code (in C# or C++) and explain your architectural decisions for a system that meets these constraints: The Grid & Elevation: The game uses a 2D isometric tilemap, but logically functions in 3D. Tiles have varying elevation levels (e.g., ground level is 0, a trench is -1, a hill is 2). Obstacles (walls, sandbags, buildings) occupy tiles and have specific height values and "material thickness" (e.g., concrete vs. wood). True 3D Line of Sight: A unit on a hill (elevation 2) should be able to see over a wall (height 1) to spot a target on the ground (elevation 0) behind it, provided the angles align. The "Defilade" Mechanic (Directional Cover): When Unit A fires at Unit B, the system must calculate if Unit B is in cover. Cover is purely directional. If Unit B is behind a half-wall relative to Unit A, they receive a defensive bonus. If Unit B is in a trench (elevation -1), they have cover against ground units, but no cover against mortar fire (parabolic trajectory). Performance: This is an RTS. Up to 300 units may need to calculate LOS and cover states simultaneously every few frames. Deliverables: The data structures for the Grid, Tiles, and Units. The math/algorithm for translating 2D isometric coordinates to calculate a 3D raycast/LOS check. The algorithm for determining if a unit has directional cover against a specific incoming attack vector. A detailed explanation of how you would optimize this to maintain 60 FPS with 300 active units (e.g., spatial partitioning, bitmasking, caching).