First of all sorry for bad english.
Now, i've played it for a while, It's a neat game but it kinda lacks complexity and features, if you're planing to extend it further ofcoarse.
Here is how i'd have done it:
1) A square game field (althought i would prefer circle) and instead of one granny - many people that are standing or walking by the borders of it, throwing popcorn.
(people can be simple meshes or even sprites - doesn't really matter). Randomizer will pick each time a different person to throw popcorn.
2) Camera probably should always be positioned and locked behind your pigeon's back and rotate along with his rotation. Keeping the same downward angle will help to avoid the need of modeling anything beyond game field itself.
3) Gameplay mechanics:
a) no machinegun - immersion breaking (well if we're taking about immersion at all, no offense), player's pigeon should have more distinctive pallete.
b) to prevent enemy pigeons from eating popcorn you'll have abilities like "push", "scream" and "sprint"(or smthn like that)
"Push" (would have cooldown, strength and stun duration parameters) will push back nearby pigeon (that was positioned in front of your pigeons head) and stun him for a little while. The higher the level the more stronger versions of enemy pigeons will spawn and pushing them will be harder/not so efficient.
"Scream" (long cooldown, radius, scatter duration) will affect all pigeons in certain radius causing them to scatter for a certain duration and thus alowing you to get popcorn while they are distracted.
"Sprint" (cooldown, duration of effect, walking speed boost) increases your speed for a short amount of time (1,5-2 sec), also during sprint if you run into some pigeon he will roll away like bowling bowl and get stunned for a while, but also slowing you down a bit.
d) when you complete a level, all % of score above 50% will be transfered to you as skill points. Between levels you can spend them to upgrade parameters of your abilities (such as upgrading strength of "Push" will grant you more chances agains stronger version of enemy pigeons and etc)
And so, the core game mechanics of the game will be:
- smart game field navigation;
- strategical timing and use of abilities;
- strong motivation to perform better in current level to gain more skill points;
Well, hope it helps :)