0 Set up Renderer
0a Set up Renderer with helper
1 Set up a renderer and render a png.
1a Scale png via destination rect
1c Render XPM with logical-render size
5 Saving a screenshot, use key s
6 uses SDL_RenderDrawPoint
to render a gradient.
7 resizes the gradient to the window dimensions
8 animates the gradient like a new shadertoy gradient.
6-8 showing a bit how glsl works and why we want shaders.