1### Compilation failed: 2 3error: 1: 'main' must return: 'vec4', 'float4', or 'half4' 4void main() { 5^^^^^^^^^^^ 6error: 2: unknown identifier 'sk_FragColor' 7 sk_FragColor = half4(sk_Clockwise ? +1 : -1); 8 ^^^^^^^^^^^^ 9error: 2: unknown identifier 'sk_Clockwise' 10 sk_FragColor = half4(sk_Clockwise ? +1 : -1); 11 ^^^^^^^^^^^^ 123 errors 13