I will decide absolutely on most of these things closer to the release date. I was just hoping to get a little bit of interest so that I could come back and get support easier. However, I do predict the following:
1. Why I, and about 15 of my friends who have seen it, think it's fun: Unlockables and secrets will run the game, pretty much. There will be at least 50 different weapons in the release version, with at least 4 different types of attack (lasers, gas, melee, bullets). These weapons will have many different types of damage and penetration, rate of attack, overheat speed, bullet speed, range, damage per shot, etc. There will be many, many different types if collectible items, which will buff/debuff stats, generate shields, allow double fire rate, decrease enemy damage, etc. Honestly, I loved The Binding of Isaac, but I wanted more, in a different style. More weapons, more items, less bugs (lol), more item types, more enemies, more levels, more mechanics, more secrets, more unlockables, more stats to keep track of, more game modes, etc. I am making it so that animations of bullets, explosions, etc are fluid, pleasing and very electronic.
2. I will be releasing updates semi-regularly with new items, weapons, secrets, enemies, etc to keep players interested.
3. I plan to release it for about $10, but if that proves slow, I will gradually decrease it to about $5.
4. I will try to make it good enough and stable enough (as it is, it has practically no bugs, although I will have beta testers) to get the game on Steam, but if it is not accepted, I will try some smaller systems like Desura.
5. The target audience would pretty much be everyone 12+, although it will be playable for younger people.
6. The number of songs is based on how many chapters I have, which will mean there will probably need to be 10-15 songs.
7. The payment rate will need to be negotiated, but will probably be quite generous.
8. PayPal is probably the way to go, but if there is a more efficient system, I will probably go for that. If the distribution system itself has a way to set that up, I will choose that option.
9. The songs will likely be loops, but if they become a bit rough at the ends, I may change my mind.
10. The emotion of most of the songs will be neutral, and it should range from (I don't know the vast majority of musical terminology) relatively peaceful, with some sort of beat, to exciting and intense, with lots of beats and dubstep elements (these will be for boss battles). There will be (likely) absolutely no story.
11. The sounds will be mostly electronic, but explosions may be at least semi-realistic. I may be able to create these sounds on my own, but if I can't, I will obviously get someone else to do it.
I hope this helps.