For this level, I made a Half-Life 2 level that could theoretically take place as a detour during the “Water Hazard” level. This would take place early on in the game, so I designed this level as an introduction to the pistol, the weapon the player recently acquired. As such, the enemies are all zombies, and although the intensity increases as the player moves towards the end of the level, it's still relatively easy shooting. Ammo management and positioning is more important, and is taught in this level.
In this level, the player is venturing into an abandoned water treatment plant to raise a gate and continue on their journey. This requires finding a valve and using it to raise the water level, to then jump on floating crates and proceed.
The level wraps around on itself throughout, bringing the player back to see previous checkpoints from a different angle multiple times. This gives the level a compact feeling without being too short, I feel, and creates a very tangible sense of progression.
Even though this is just a whitebox, I tried to include some instances of environmental storytelling. As the player progresses towards the executive's office, it becomes clear the higher-ups at the facility didn't fare well during the zombie outbreak.