For a game that takes place in imagination 'world' the game is surprisingly devoid of it.
Same elements are being used in levels several times (formations) and there where nothing truly surprising. bosses where at positive side, had partial areas you could destroy before the 'core' of the boss. but othervice none of the where truly difficult either. Moneybalance could use revamp as well, as in later levels you get only tiny amount of money from both bosses, and other more durable enemies. in one case same level had 2 different type of walls, and weaker one gave more reward than more sturdy one that possessed more of a threat (by blocking flight path)
music was very repetitive and loop was quite far from seaming-less. every world has same basic music throughout the game, and while bosses had their own theme, they too shared the same music between themselves. the contra power-up had some music clip, but i never truly heard it well enough, thanks to the basic music being too loud compared to that. In future more musics are definitively needed and should be made seaming-less loop as possible.
by graphic side the game had put some effort to them, and tough some enemies and maps had othervice dull layout, graphic themselves where nice "8-bit" or pixel type you could expect.
game play was very simple as well and required almost no learning of controls, thanks to the mouse control. character followed the mouse almost without a delay. this allows sometimes rather absurd evasive maneuvers but game play self suffers very little because of it. In later levels the enemies however spent half of their time outside the screentop, outside the reach of your bullets and other power-ups and hate power attacks. in one level few of them stayed there over one and half minute, shooting their bullets until the time ran out that the wave was complete. this would be something i would like to point you to look at in future games. ,
tough this game offers "hardcore" player very little challenge, this goes well for casual players who enjoys games that are neither tedious or unforgiving.