1### Compilation failed: 2 3error: 14: 'main' must return: 'vec4', 'float4', or 'half4' 4void main() { 5^^^^^^^^^^^ 6error: 17: unknown identifier 'sk_FragColor' 7 sk_FragColor.r = half(a1.x) + half(b1.x); 8 ^^^^^^^^^^^^ 92 errors 10