Aye, it is a hard game, but it should be completable. Especially when i give the bosses levels of their own. Every ordinary level is going to end with a special encounter though, meaning a pack of the new/upgraded enemy you'll see in the next level. Not nearly as hard as a boss, but still enough to provide a sense of surprise. HOWEVER, no lives will be provided, but at least you can try as many times as you want. You'd just have a limited number of retries if you had lives. I'd hate that myself.

Also, i'm nearly done with level 2, but the new enemy type is currently giving me hell. But when it's done, you'll get a new demo, which is a little bit easier to complete.