Some advice for new players, this is a play it until you die kind of game, with only 3 enemy types to fight, so once you’ve killed everything and maybe upgraded everything, you’ve seen everything.
Of the upgrades, the explosive rounds is the worst. Try and get the double gun, then the advanced bench and the final gun. AP gun is also useful for one of the enemy types.
To the developer, an ending would be nice, or some incentive to keep playing, like a score or something. Pick something arbitrary, like ‘it will take 100 days to reach safety’, but a game that doesn’t is a game that’s never finished.