// Multikey input helpers.
bool check_key_down(array<int>@ keys) {
    // True when at least one key in the set is currently down.
    if (keys is null || keys.length() == 0) {
        return false;
    }

    for (uint keyIndex = 0; keyIndex < keys.length(); keyIndex++) {
        if (key_down(keys[keyIndex])) {
            return true;
        }
    }

    return false;
}

bool check_all_keys(array<int>@ keys) {
    // True only when every key in the set is currently down.
    if (keys is null || keys.length() == 0) {
        return false;
    }

    for (uint keyIndex = 0; keyIndex < keys.length(); keyIndex++) {
        if (!key_down(keys[keyIndex])) {
            return false;
        }
    }

    return true;
}