These should all be valid:
@supports (color: green): PASS
@supports (color: green) and (width: 50px): PASS
@supports (color: green) or (flogwizzle: purple): PASS
@supports (not (flogwizzle: purple)): PASS
@supports selector(.simple): PASS
@supports selector(a#more > .complicated.case:nth-child(42)): PASS
@supports selector(.easy) or selector(.....nope): PASS
@supports env(preferred-text-scale): PASS

These should all be invalid:
@supports (not (color: green)): PASS
@supports (color: green) and (width: 50px) or (color: green): PASS
@supports (width: yellow) or (height: green): PASS
@supports (flogwizzle: purple): PASS
@supports selector(.....nope): PASS
@supports selector(::-thing-we-dont-support): PASS
@supports selector(32) or selector(thing[foo??????bar]): PASS
@supports env(florb): PASS
@supports env(123): PASS