Bouncing Ball Demo for SolarSail

A simple demonstration of SolarSail's entity-component system showing a ball bouncing around the screen edges.

What It Demonstrates

• SolarSail's coordinate system (origin at center)
• Entity creation with components
• Script components with on_init() and on_update()
• Transform manipulation
• Sprite rendering with atlas
• Basic physics and collision detection

Custom Ball Sprite

The demo includes a custom 3D-looking red ball created with SVG:

1. Created SVG (ball_transparent.svg):

   • Radial gradient from white highlight to bright red (#ff6b6b) to dark red (#c92a2a)
   • White highlight ellipse for shine effect
   • Subtle shadow underneath
   • 64x64 pixel dimensions

2. PNG Conversion with Transparency:

   • ImageMagick's convert command failed to preserve transparency properly
   • Solution: Use Inkscape for SVG to PNG conversion

   inkscape ball_transparent.svg --export-type=png --export-filename=ball.png --export-width=64 --export-height=64

3. Atlas Creation:

   • Copy ball.png as atlas.png (single sprite atlas)
   • Update atlas.lua to define one sprite named "ball"

Running

cd /home/dagostinelli/projects/solarsail/bouncingball
make run

Press 'q' to quit.

Key Files

• program.lua - Engine callbacks and window creation
• game.json - Scene definition with ball entity
• ball.lua - Ball physics and movement logic
• config.lua - Screen bounds and ball parameters

Important Concepts

1. Coordinate System: Origin (0,0) is at screen center
2. World Coordinates: X: -1.78 to +1.78, Y: -1.0 to +1.0
3. No dt parameter: on_update() doesn't receive delta time
4. Transform property: Use transform.translation, not transform.position

See GETTING_STARTED.md for a detailed tutorial.