struct VertexOut {  @builtin(position) position : vec4f,  @location(0) color : vec4f } @vertex fn vertex_main(@location(0) position: vec4f,  @location(1) color: vec4f) -> VertexOut {  var output : VertexOut;  output.position = position;  output.color = color;  return output; } @fragment fn fragment_main(fragData: VertexOut) -> @location(0) vec4f {  return fragData.color; }