# bglga

This project is a simple Galaga-like space shooter game built using the Bevy engine.

## Current State

The game features:

*   A player ship at the bottom of the screen that can move left and right.
*   Shooting bullets upward using the spacebar or up arrow key.
*   Enemy ships that spawn at the top and move downward.
*   Collision detection between bullets and enemies.
*   **Collision detection between the player and enemies.**
*   **A player lives system (starting with 3 lives).**
*   **Player destruction upon collision.**
*   **Player respawn after a short delay with temporary invincibility.**
*   **Remaining lives displayed in the window title.**

## Controls

*   Move Left: A key or Left Arrow
*   Move Right: D key or Right Arrow
*   Shoot: Spacebar or Up Arrow

## How to Compile

```
nix develop --command bash -c "cargo build"
```

## How to Run

1.  Make sure you have Rust and Nix installed.
2.  Clone the repository.
3.  Navigate to the project directory.
4.  Run the game using the command: `nix develop --command bash -c "cargo run"`

## Headless Screenshots

The flake exposes a `take-screenshots` app that launches a binary inside an
Xvfb display backed by lavapipe (software Vulkan), waits, and captures one or
more PNG screenshots. Useful for smoke-testing rendering without a real GPU.

```
nix run .#take-screenshots -- EXE NUM DELAY_START PAUSE_INBETWEEN [OUTPUT_DIR]
```

*   `EXE` — path to the executable to launch
*   `NUM` — number of screenshots to take
*   `DELAY_START` — seconds to wait after launch before the first shot
*   `PAUSE_INBETWEEN` — seconds between consecutive shots
*   `OUTPUT_DIR` — where to write `shot-NNN.png` files (default: current directory)

Example, capturing three frames of the game one second apart after a six-second
warm-up (Bevy + software Vulkan needs roughly that long to render its first
frame):

```
cargo build
nix run .#take-screenshots -- ./target/debug/bglga 3 6 1 ./shots
```