Very repetitive and took a long time to get to try the various upgrades. Entertaining but gets tedious doing the same moves over and over to get enough cash to upgrade.
Another suggestion would be to have the anti-matter shield require the static shield first and have it drain energy when in use. That way if you rely on it too much you run out of energy and can't use the shield anymore. Would make it more strategic. Or have it that the anti-matter shield only blocks a percentage of the damage you would have normally taken.