type fixture : t {
    predicates {
        fixture_requires(fixture, o);
        reveals_item(fixture, o);
        reveals_readable(fixture, readable);
        hidden_readable(readable);
        sealed(fixture);
        fixture_keeps_use(fixture);
        fixture_consumes_use(fixture);
    }

    rules {
        use/fixture/item/keep :: $at(P, r) & $at(fixture, r) & sealed(fixture) & $in(o, I) & $fixture_requires(fixture, o) & $fixture_keeps_use(fixture) & stored_item(o') & $reveals_item(fixture, o') -> at(o', r);
        use/fixture/item/consume :: $at(P, r) & $at(fixture, r) & sealed(fixture) & in(o, I) & $fixture_requires(fixture, o) & $fixture_consumes_use(fixture) & stored_item(o') & $reveals_item(fixture, o') -> at(o', r);
        use/fixture/readable/keep :: $at(P, r) & $at(fixture, r) & sealed(fixture) & $in(o, I) & $fixture_requires(fixture, o) & $fixture_keeps_use(fixture) & hidden_readable(readable) & $reveals_readable(fixture, readable) -> at(readable, r);
        use/fixture/readable/consume :: $at(P, r) & $at(fixture, r) & sealed(fixture) & in(o, I) & $fixture_requires(fixture, o) & $fixture_consumes_use(fixture) & hidden_readable(readable) & $reveals_readable(fixture, readable) -> at(readable, r);
    }

    reverse_rules {
        use/fixture/item/keep :: use/fixture/item/keep;
        use/fixture/item/consume :: use/fixture/item/consume;
        use/fixture/readable/keep :: use/fixture/readable/keep;
        use/fixture/readable/consume :: use/fixture/readable/consume;
    }

    inform7 {
        type {
            kind :: "fixture-like";
            definition :: "fixture-like is a kind of thing. fixture-like is fixed in place.";
        }

        predicates {
            fixture_requires(fixture, o) :: "";
            reveals_item(fixture, o) :: "";
            reveals_readable(fixture, readable) :: "";
            hidden_readable(readable) :: "";
            sealed(fixture) :: "";
            fixture_keeps_use(fixture) :: "";
            fixture_consumes_use(fixture) :: "";
        }

        commands {
            use/fixture/item/keep :: "use {o} on {fixture}" :: "unlocking the {fixture} with the {o}";
            use/fixture/item/consume :: "use {o} on {fixture}" :: "unlocking the {fixture} with the {o}";
            use/fixture/readable/keep :: "use {o} on {fixture}" :: "unlocking the {fixture} with the {o}";
            use/fixture/readable/consume :: "use {o} on {fixture}" :: "unlocking the {fixture} with the {o}";
        }

        code :: """
            Understand "use [something] on [something]" as unlocking it with.
        """;
    }
}