Since my last entry, I've worked out the level design through six levels worth.  During that time, I added a few more food types and features that I thought would add some variety to the game:

• Added cherries, oranges, and pears -- purely for variety.
• Added bananas, which make the snake shrink instead of grow.  If the snake shrinks down to just a head and tail, it takes a small amount of damage.
• Added a new trigger for spawning food and danger items based on whether any part of the snake occupies a region on the map.

Not representative of how many food items will actually spawn (I was just testing things out here), but here's some bananas!

All of the various triggers, and the effects food have on the snake, are working out nicely I think.  It makes for some fun game play, and fun moments with the sound triggers in the mix.  I've been organizing the level design in "groups of 3" -- there's sort of a running theme for three levels, and then I try to change things up.  The first three levels have relatively open maps, with an increasing number of barriers.  Then things change at level 4, where the maps look at little more like the above -- long channels the player has to navigate through and around.  At level 7, the maps will change again, etc.

One thing I did come across when adding sound effects triggers though...  It's entirely possible they will overlap.  This doesn't work well if the intent is to have narration from some off-screen character, which is exactly what I'm doing.  I can end up with the same character saying multiple lines simultaneously.  So I'll be looking into how to deal with that before I release.  I'm thinking triggered sounds should be placed in some kind of priority queue.

After recording some of the dialog for the triggered sounds across several sessions, I realized I'll probably need to re-record all of in one go when the campaign is complete.  My voice tends to change in timber slightly depending on the time of day, how I'm feeling, etc.

I'm also considering whether to add the concept of "lives" into the mix.  My original thinking was if you lose all your health, that's it -- the campaign would be over.  Play testing has made me reconsider this.  I'm also thinking it would be neat to give players another reason (besides just getting the highest score for bragging rights) to score points, by having some threshold at which the player gains an extra life.