Half-Life 2 – Reactor Cooling

Half-Life 2: Reactor D6 | Level Jam | Hammer | 2022

This level was my entry into Steve Lee’s second level design jam. The themes for the jam were “Non-Violence” and “Verticality“. I decided to learn the Hammer Editor for this one as its still one of the best pure level design tools and allowed more time to concentrate on building and scripting the level. I tried to keep my scope small and focused, as time was limited.

Level Design work

  • Collected reference, designed level layout and planned gameplay beats
  • Created level blockout inside the Hammer++ editor
  • Conceptualized and scripted puzzles, interactions & environmental storytelling

Gameplay & narrative beats, intensity and level flow

Fig.1 – Level timeline 

Gameplay & beats

  1. Arrive at the reactor
  2. Wooden planks blockade
  3. Water valve and crowbar puzzle
  4. Broken stairs blockade
  5. Collect the Zero Point Energy Field Manipulator (Gravity gun)
  6. Discover the multi-level structure
  7. Exit level


Fig.2 – Level layout

Design decisions

Composition & signposting

To make use of the verticality theme, I decided to start the player up high to allow them to assess their options and decide on a path. Using this approached allowed me to stimulate the players curiosity and explore the space. I also included a windmill as a landmark to guide the player throughout the level.


I used the classic Bait & Switch technique to draw the player to an obstructed opening which blocks their path. Players can see that the crowbar is located on access walkway above them and they need to reach it. Backtracking, players can find the valve to raise the water level.


The use of gating was used to make the player stop and think about the crumbled stairway problem. The locked door implies that something the player needs is behind it. Affordances associated with scattered wooden planks and metal panels in HL2 provide multiple options for the player to progress.

Planning & Reference

The image gallery below shows some initial sketch work before block-out along with some reference imagery.

Gallery 1 – Initial sketches for the level’s layout

Fig.1 – Moodboard/concept reference

Jam video