prometeu-runtime/discussion/lessons/DSC-0001-runtime-learn-legacy-import/LSN-0012-mental-model-input.md

id	ticket	title	created	tags
LSN-0012	legacy-runtime-learn-import	Input Mental Model	2026-03-27	migration tech-debt

Input Mental Model

Status: pedagogical Companion spec: ../specs/06-input-peripheral.md

PROMETEU treats input as sampled state, not as an asynchronous event.

State Versus Event

The most important model to understand is:

• a button does not "fire" an action by itself;
• a button changes state;
• the game reads that state during the frame.

That looks much more like classic console register polling than like modern UI callbacks.

Why This Matters

This model:

• improves determinism;
• simplifies replay;
• makes debugging easier;
• makes the frame loop easier to read.

It also fits PROMETEU's identity better as a machine strongly inspired by retro hardware and DIY construction.

Good Habits

• read input in UPDATE;
• map actions, not physical keys;
• separate input reading from heavy logic;
• treat polling as part of the frame budget.

Teaching Value

The input peripheral helps teach:

• the difference between state and event;
• temporal sampling;
• synchronization between input and logic;
• determinism in interactive systems.