DVD Screensaver (Ashley ECS Edition)

A learning project built with LibGDX to practice the Entity Component System (ECS) architecture utilizing the Ashley framework

The project simulates the classic bouncing DVD logo screen, incorporating a "health" system that penalizes the logo when it impacts screen boundaries, and dynamically updates a UI health bar.

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Architectural Overview (ECS Breakdown)

To keep data separated from logic, this project splits the implementation into pure data buckets (Components) and iterative processors (Systems).

Components (Data)

• PositionComponent / VelocityComponent: Tracks the 2D coordinates and speed vectors of moving elements.
• LogoComponent: Holds the texture reference and physical dimensions for rendering the DVD logo.
• HealthComponent / HealthBarComponent: Monitors the structural health state and maps out the dimensional boundaries for the UI health rendering.

Systems (Logic & Rendering Order)

Ashley executes systems sequentially based on registration order. The layout ensures physics and rules process before visual output:

1. BounceSystem: Evaluates boundary collisions against WORLD_WIDTH and WORLD_HEIGHT, handling the directional deflection logic.
2. DamageSystem: Checks collision states and decrements health attributes upon boundary contact.
3. DeathSystem: Resolves zero-health states, acting as a reset mechanism that repositions the entity and penalizes its velocity.
4. RenderSystem: Draws the foundational game world layers (the DVD logo texture).
5. HealthBarRenderSystem: Renders user interface elements on top of the world layer, preventing the game world textures from overlapping UI components.

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Performance & Batching Optimizations

Unlike basic implementations that flag draw states per-entity, the render systems override the core engine update cycle:

• Batch Flushing Minimization: SpriteBatch.begin() and end() are triggered exactly once per system cycle rather than per-entity. This packages all drawing operations into single draw calls, drastically lowering CPU-to-GPU overhead.
• Memory Management: UI assets (like health bar background/foreground panels) utilize low-overhead single-pixel Pixmap textures generated and cached natively at startup to eliminate real-time I/O lag.

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Getting Started & Execution

This project uses Gradle to manage dependencies. The Gradle wrapper is included, so you can run Gradle tasks using gradlew.bat or ./gradlew commands.

Core Commands

• Run the Desktop Application:

  ./gradlew lwjgl3:run

• Build an Executable JAR: (Outputs to lwjgl3/build/libs)

  ./gradlew lwjgl3:jar

• Clean Build Directories:

  ./gradlew clean