The Empty Room
For months, the engine was a technical exercise. Vulkan pipelines, ECS architecture, asset importers, VPak packaging — all impressive infrastructure with nothing to play. The engine could render models, play audio, and load levels, but it wasn't a game yet.
That changed on a Saturday in early March.
Physics-Based Movement
The first task was player movement. Not just "move left when you press A" — real physics-based movement with momentum, friction, and groundedness detection. The player is a cat, and cats don't move like FPS protagonists. They accelerate, they pounce, they land with weight.
The implementation used a rigidbody dynamics model:
- Groundedness raycast: A downward ray from the player's center detects contact with the ground. This drives the animation state machine and friction coefficients.
- Acceleration model: Input doesn't set velocity directly — it applies acceleration. Friction decelerates when input stops. This gives movement a sense of weight.
- Jump arc: Jump is an impulse, not a teleport. The arc is determined by gravity and initial velocity, not by a scripted curve.
HFSM Animation
The animation system uses a Hierarchical Finite State Machine (HFSM). States like Idle, Walk, Run, Jump, and Land are organized hierarchically — Grounded is a parent state containing Idle, Walk, and Run; Airborne contains Rising and Falling.
The HFSM syncs with the physics state. When groundedness flips from true to false, the animation transitions from Grounded to Airborne. When velocity-y flips from positive to negative, Rising transitions to Falling. The physics drives the animation, not the other way around.
The Cat That Could Jump
By evening, the prototype was running. A textured cat model standing on a flat plane. Press D — the cat walks right, with acceleration and footstep audio. Press Space — the cat jumps, arcs through the air, and lands with a separate landing animation. The camera follows smoothly, with slight lag and vertical look-ahead.
It was the simplest possible game — a cat on a plane — but it felt alive. The weight of the movement, the responsiveness of the jump, the way the animation matched the physics state — for the first time, the engine wasn't just rendering triangles. It was playing.
That's the moment you know an engine is real: when you forget you're testing and start just moving the character around because it feels good.
What Came Next
The prototype validated the architecture. Physics, animation, audio, input, camera — all the systems worked together through the ECS framework. Adding levels, VFX, and gameplay mechanics from here was incremental, not foundational. The hard part was done.
Everything since that Saturday has been building on the foundation that the side-scroll prototype proved was solid.