Juan Esteban Rayo Contreras
Passionate game developer, math nerd and avid gamer. My love for videogames goes beyond measure. Just trying to be the best developer that I can be, so I can make the people feel the same way I feel when I play videogames .
I am not scared of failure and proposing new ideas. I am always hungry for knowledge.
I love RPGs. and soulful games ( Mass Effect, Stardew Valley, Final Fantasy 6 - 7, Balatro, Factorio).
Passionate for Game Engine and Gameplay Programming.
Skills
Almost 6 years of professional game development.
→ Advanced knowledge of C++ :
● C++ 11, 17, 20.
→ Knowledge of C#.
→ Advanced professional knowledge in Unreal Engine :
● Multiplayer
● C++
● Blueprints
● Gameplay Ability System
● 3D Math.
● Core Engine Knowledge.
→ Game Engine Programming ( Ishak Engine ) :
I am really passionate about game engines because I think that game engines are the heart of a game and by creating them, the bricks for the dev team are being made, so they can build the best game possible for the players!
● I am making my own game engine from scratch in C++ just for fun.
● Making a custom Build Tool (Ishak Build Tool) in C# for the engine, it will build the environment for the development of the project. It will include features like: compilation features, pre-build, post-build, dependency solving, cooking...
Experience
→Engine Programmer - Neural AI (Aug 2025 - October 2025)
Custom Engine
● Worked on improving the engine job system (multiple producer-multiple consumer)
● Implemented memory tracking for the memory allocators in the engine.
● Worked on the implementation of the V8 library in the engine with a zero-copy memory paradigm, so V8 directly
modifies that C++ memory.
● Worked in the first iteration of the network library, adapting the yojimbo lib to the engine needs.
→ Gameplay Engineer - 31st Union(2K Games) (Aug 2023 - August 2025)
Unreal Engine 5
● Working on a AAA game: Project Ethos.
● Worked on core Ability System features for developing new abilities for the current game we are developing.
● Extended the Core Telemetry System for in-game abilities.
● Collaborated with designers for creating new Gameplay features along new systems that helps the Art and VFX teams to implement new features
● As a member of the Core Engine team, developed a tool for the sound team so they could modify a GoogleSheet and import data directly to the Engine.
→ Gameplay Engineer - The Breach Studios (Sept 2021 - Aug 2023)
UE5 + external custom Engine framework in pure C++ 17.
● Worked on multiple core gameplay systems extending the Engine when needed( UE5 ):
I developed all the systems following a TDD approach and using pure C++ code and then implemented the Framework in the Unreal Engine, so all the logic was already tested when implemented. Every system was architectured for reusability and extension if needed.
All the logic for the systems are interfaced through Unreal Engine objects so the logic is decoupled from the implementation when implemented.
→ Interactable System: Implemented a core system that handled interactable entities in the game, it could be from a teleporter to a land mine that landed damage to a character:
● ECS architecture ( used various systems and components for handling the interaction between player - interactable ).
● Network replication using our custom pure C++ framework.
→ Deployable System: Implemented system for the Gameplay Team that handled different turrets and entities called deployables and its interaction with the player.
● ECS architecture.
● Network replication using our custom pure C++ framework.
→ Loadout System: Implemented system for the player loadout customization, so every player had everything they selected in the lobby in-game.( Character, skins, weapons, weapon skins... )
● Used Data From backend to create the Loadout Data.
● Handled communication between client-server for handing the player Loadout selection( when they selected X skin or character ).
● Handled Backend validation on server for verifying the clients' loadout selection.
→ Software Engineer - Quantum One Studios ( February 2021 - May 2021)
Unreal Engine 4
● Working on an unannounced Online game.
● Implemented all the systems of the Game:
→ Multiplayer System (Lobbies, Online Subsystem Implementation, Player preferences ...).
→ Gameplay Systems (Camera, Weapon, Hit registration, Character Attributes, Animation ...).
→ Gameplay Engineer - Limitless Games (May 2021 - August 2021)
Unreal Engine 4
● Worked on the Game Abilities for the different character classes using the GAS (Gameplay Ability System of Unreal Engine).
● Provided a system for the designers to change the ability values from outside the project.
● Developed part of the Ability System that the game required.
→ Gameplay Engineer - Hidden Leaf Games ( January 2020 - February 2021)
● Worked and implemented algorithms for the gameplay ( In-game Items, Abilities Replication for the Server-Client Interaction )
● Implemented the base ability logic for all the abilities.
● Designed and implemented systems for the designers' interaction with the gameplay.
● Rigged the Animations for the character in classes.
● Worked on the Math Library of the project.
NOTE: Click on every image to follow the link associated with the game.
● Project Ethos - 31st Union(2K)
● Mayor contribution to FANGS - (Steam)(2023) - Hidden Leaf Games
● Ascendants Rising - (Steam) (2021) - Limitless Games.
● Project ST - (2024) - The Breach Studios.
Shipped Games
