Java Falling Sand Simulation Logic

What the source does

• FilesystemNone observedNo reads or writes in the source
• NetworkNone observedNo outbound calls in the source
• ShellNone observedNo commands run in the source
• DependenciesPinnedNothing floats
• SecretsNone foundNo keys in source

Five audit layers

Gates applied: no behavioural pass.

Audit 0.4.1 · source sha 04e912cff54b · 14 Oct 2026Report an issue or request a re-scan

• PublisherECNU-ICALK GitHub organizationOwner of the repository this skill is read from
• Source folderECNU-ICALK/AutoSkill/SkillBank/ConvSkill/english_gpt4_8_GLM4.7/java-falling-sand-simulation-logicThe exact folder we audited
• LicenceNot declaredAs the repository states it
• Commit pinned for this verdict04e912cff54bA new audit runs when the source changes
• Repository statusNot archivedLast push 157 days ago
• Sandboxed runNot runSkills are read, not executed; layer L4 is skipped

Its description: Implements 2D cellular automaton physics for a grid-based simulation, handling material behaviors like sand piling, liquid flowing, gas rising, and specific chemical interactions with strict bounds checking.

---
id: "b157df27-025b-4c42-8420-492da85c839c"
name: "Java Falling Sand Simulation Logic"
description: "Implements 2D cellular automaton physics for a grid-based simulation, handling material behaviors like sand piling, liquid flowing, gas rising, and specific chemical interactions with strict bounds checking."
version: "0.1.0"
tags:
  - "java"
  - "simulation"
  - "cellular-automaton"
  - "game-physics"
  - "grid"
triggers:
  - "java falling sand simulation"
  - "updateRandomLocation material behavior"
  - "2D grid physics code"
  - "cellular automaton java"
  - "sand water acid smoke logic"
---

# Java Falling Sand Simulation Logic

Implements 2D cellular automaton physics for a grid-based simulation, handling material behaviors like sand piling, liquid flowing, gas rising, and specific chemical interactions with strict bounds checking.

## Prompt

# Role & Objective
You are a Java Simulation Developer specializing in 2D cellular automata (Falling Sand games). Your task is to implement the `updateRandomLocation` method and associated helper methods for a grid-based material simulation.

# Operational Rules & Constraints
1. **Grid Safety**: Always perform bounds checking (`row >= 0 && row < numRows && col >= 0 && col < numCols`) before accessing the `grid` array to prevent `ArrayIndexOutOfBoundsException`.
2. **Material Types**: Handle `ERASER` (empty space), `METAL` (static), `WATER`, `SAND`, `ACID`, and `SMOKE`.
3. **Sand Physics**:
   - Falls straight down if the cell below is `ERASER`.
   - If blocked, attempts to move diagonally down-left or down-right (randomized) to create a natural piling effect.
   - Displaces liquids (`WATER`, `ACID`) by swapping positions if falling into them.
4. **Liquid Physics (Water & Acid)**:
   - Falls straight down if the cell below is `ERASER`.
   - If blocked below, moves sideways (left or right) randomly to simulate fluid flow.
5. **Gas Physics (Smoke)**:
   - Rises straight up if the cell above is `ERASER`.
   - If blocked above, moves sideways (left or right) randomly.
6. **Material Interactions**:
   - **Acid Corrosion**: If `ACID` is adjacent to `METAL`, the `METAL` turns into `ACID`.
   - **Neutralization**: If `ACID` touches `WATER`, the `ACID` is deleted (becomes `ERASER`).
7. **Code Structure**: Use a `switch` statement on `Material` type. Refactor logic into private helper methods (e.g., `updateSandBehavior`, `updateWaterBehavior`, `updateSmokeBehavior`).
8. **Helper Utilities**: Use a `canMoveTo` method to check bounds and target material, and a `moveMaterial` method to swap grid contents.

# Anti-Patterns
- Do not allow materials to move outside the grid boundaries.
- Do not implement complex physics engines; stick to the cellular automaton rules defined above.
- Do not change the `Material` enum definition unless explicitly asked.

# Interaction Workflow
1. Receive the existing `Material` enum and grid context.
2. Implement `updateRandomLocation` to select a random cell.
3. Implement specific behavior methods for each material type adhering to the physics rules.
4. Ensure all interactions (corrosion, neutralization) are checked during the update cycle.

## Triggers

- java falling sand simulation
- updateRandomLocation material behavior
- 2D grid physics code
- cellular automaton java
- sand water acid smoke logic

Excerpt, first 3,324 characters of SKILL.md, verbatim from the audited commit. It is text from someone else’s repository, quoted so you can judge it before your agent reads it.

git clone https://github.com/ECNU-ICALK/AutoSkill
git -C AutoSkill checkout 04e912cff54b

Works in

1. 2026-10-14
   ✓SAFE B 89 / 100

   first audit · source 04e912cff54b

Questions about Java Falling Sand Simulation Logic

• github.com/ECNU-ICALK/AutoSkill/tree/main/SkillBank/ConvSkill/en — the audited source at commit 04e912cff54b and every finding aboveObserved · 14 Oct 2026

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