We are starting to see some diversification in enemies, which is good. The first several monsters are a bit bland. Some more ideas (for enemies, mechanics, items...):

• New monster: suicide bomber. The explosion should be quite small but still dangerous up close. Perhaps more importantly, it should harm other monsters. If that's too redundant (too many explosions), they could just burst in a pool of slime spreading across the floor, then drying up after a few seconds.

• Flying enemies. They could include melee attackers and bombers. Bombers should make significant damage to the terrain. It could be interesting to introduce a new shooting key: "shoot upwards". It would be "5" on numeric, and for everyone else... hmm... I guess 1 more key isn't that much, right ?

• enemies that shoot projectiles like artillery, in an arc.

• gremlin: a helpful "enemy" that runs away from the player. Like scarabs in Spelunky, they would have to be picked up. This would grant a random powerup, including Duplicate, Apple, Chocolate and Sushi. As for introduction of new powerups affecting old levels... room creators could have two settings for gremlins. a) progressive: gremlins in this room will be affected by future changes. b) conservative, the list of possible powerups will be limited to those available in current version.

• a DooM-style explosive barrel. This means an immobile barrel that explodes when shot. The explosion should probably be the half of a robot death/boom powerup in radius. Otherwise the room will be destroyed in a moment with a few of those. (Alternative implementation - an old-fashioned spherical bomb that ignites when shot, exploding shortly after. The point - you could push it with gunfire giving a little control over where it explodes)

• A boss: huge spider with loooong legs. To win, the player would have to cut all his legs little by little, finally lowering its torso to the same level. Only then you could shoot the torso (unless vertical shooting is implemented, I guess).

• a boss: pair of chargers/rollers. The violet creatures that curl up in a ball. "Charger Twins" boss would be just like them, but with much more HP. Also, there would be an energy beam between charger1 and charger2. Player would have to be on his toes and quite often jump over the beam. Bonus points for making each charger a different color... or even randomly generating their colors.

• some kind of explosive weapon, a rocket launcher or a grenade launcher with bouncing projectiles (Quake style). Sorry, but Blaster doesn't cut it.

• speaking of Blaster, it it's a bit unsatisfying to use. It is okay against big enemies, but I think at least a cool visual upgrade is warranted.

• new powerup: Force. Just like normal rounds, but pushes enemies away AND pulls powerups closer. Duration - not sure, 99 might be okay.

• new powerup: orbiting shield. It could have the same kind of duration limit as Sword of Fortune (until you get hit). It would work like a projectile circling around the player.

Wow, some cool ideas. I particularly liked your dual charger boss concept!

• Gargoyle mode for monsters. Until triggered, they are invulnerable (but solid). Visually, they would be made entirely of 1 color (chosen by level creator). Especially mean level designers could place a number of them in lava (trigger: proximity) forcing player to quickly jump across the pool of of lava before gargoyles fully materialize (and stop acting as a makeshift bridge).

• New monster: shielder. Completely indestructible from 1 side, soft from all others. Can never rotate (but can move and harm player normally). Optionally, they could even reflect missiles that hit their shield.

• New environmental effect: Acid rain. Basically the opposite of Snow, it would slowly eat away at terain. A form of soft time limit on levels with fragile architecture.
  About environment in general - I'm a bit sad that environment overrides floor setting. For example I chose Dirt, which is brown and would contrast with fresh snow. Except it makes all surfaces covered with snow. A nice effect visually, but a bit limiting.
  It would be nice to be able to trigger weather effects.

• New monster: turret. There could be two types: one that faces a single direction and acts as a trap. Second would be omnidirectional, and shoot like red monsters do. It could look like a statue.

• new weapon: Railgun ! Not like in Predator (where it supposedly explodes), but more like in Quake where it cuts through multiple enemies in a single line. Hitscan weapon, slow rate of fire, leaves visible beam. Only in Voxatron, it could actually perforate terrain.

Nice Ideas

I would like to see two kinds of Swords.
The golden known Sword of Fortune as the most powerful sword and a weaker Sword of Barbarian which stays permanent for some longer Barbarian area fights until death or pickup of a new shooter-power-up. . Imagine some brown leather armor with this circlet from Connan the barbarian.

I love these ideas. Simply amazing.

re: turret idea

I've seen one or two BBS levels that sort of use a 'trick' to do this already. What you do is make a small pit, but make it fairly deep. Then you set the enemies with SUPER long legs that fire beams at you to spawn inside that pit. They can't get out, and you have a fully-functional turret!

some sweet ideas. i guess it will only be a matter of time till they all happen :D... I mean voxatron is going to become an engine of the voxatron-universe essentially right? So any ideas would be possible... for example, create acid rain yourself then instruct it to eat at the terrain?

I love those ideas, but now, i'm worried about how the enemy editor will work - I hope it won't be only editor for looks, but you would be also able to edit speed, type of attacks(there should be some really complex settings), etc...

a lot of great ideas. hopefully they will add actor editor and scripting so we can make our own monsters and players

Really great ideas. I'm especially partial to b0rsuk's "gargoyles" and the idea of having fixed and rotating turrets. I also think the grenade launcher in combination with indestructible terrain would make for some interesting gameplay (like a challenge in which the player has to bounce the grenade through a small opening in order to destroy an enemy on the other side of a wall).

Additionally, I think enemies that replicate themselves would be a good idea, either splitting over time or when shot, shrinking and multiplying until they reach their smallest size where they can be destroyed.

More ideas...

• Gauntlet-style monster generator ! This means a structure that produces one specific monster at a fixed interval. Diablo2 also has them. Of course, works only until destroyed !

• New powerup: Recolor. All voxels on the level change their color. No gameplay effect at all. The game "Spheres of chaos" has such a powerup. (all voxels of one color are changed to the same color, ROT13 etc)

• New object: jump pad. You step on it, it bounces you. Monsters would also be affected. Ideal method for transporting minotaurs. Rollers would love it.

• Fragile objects. Basically the opposite of indestructible objects. Upon taking minimal damage, the entire object falls apart. This would be useful for items like glass windows.

• New powerup: Targeting System. Shots fired by player automatically adjust their vertical angle, much like in DooM without mouselook. This means you can easily shoot enemies that are not on the same level as you... while it lasts.

• new item: monster food. Inspired by the game "Gremlins". These would be items that monsters can consume to become nastier versions of themselves. Orange imps (or whatever they are) would become purple (jumping) imps. Orange grunts would become red grunts (shooting). Blue ankle biters/swarmers would become white or brown ankle biters (jumping).

• new weapon: Thunderbolt. Continuous beam of electricity. Powerful, but low ammo, and can't be controlled. It would automatically hit the closest monster. So not just "easier aiming", but rather "no aiming", at all ! You only press the button. This would be a downside in situations where some nasty monsters need to be eliminated quickly.

• new weapon: Minigun. Very powerful, but inaccurate over long ranges. There would be spin-up and spin-down time, and it would severely slow you down while firing (and we know how dangerous not moving is in Voxatron !). It would require a little skill to use, because you'd become an easy target for fast monsters and shooters.

I am for indestructable and fragile objects. As we're all rather forced to use destructable voxels even as "NPCs" and "doors" at present (which also still work despite being destroyed), and the very walls of every indoor area can be made to collapse if you shoot through it from every angle.

Speaking of which, there isn't a way to remove objects after they're spawned... For such an NPC to "move" you currently have to either just spawn more stuff on top of it, or change to another map.

Granted, this has been done to amazing effect so far in a few of the more beautiful works I've seen here, but still...

It's also rather annoying that all voxels/props are completely solid, right down to the leafy part of a vegitable garden. If we're extending the format to support different types of voxels, don't leave that out.

I agree that destruction gets a little excessive at times. Not just destruction, with a few snails level exit can become completely lost.
firehand94 had an interesting idea in another thread. Voxels could have health, some materials would be harder to destroy. I don't know if it wouldn't suddenly make the game consume too many resources. While it does sound a bit like arkanoid/breakout, it would allow quite a bit of flexibility.

There's one danger about indestructible and fragile objects, however. Nothing forces the map creator to place exits in sensible places and sometimes it's hard to guess where to go. It could get much worse if suddenly we have to guess which walls are destructible and which not ! Red Faction syndrome ?

Paratrooper (monster flag)
Monsters with this flag don't spawn on the ground. Instead, they just fall from the sky. This could be a fun variation and would play slightly differently, you could run below them.

Software Glitch (negative pickup)
A negative pick up item along the lines of Duplicate. Software Glitch would temporarily disable diagonal movement (and shooting?). Alternatively, it could work until you get hit. Either way, the effect would be indicated by flying sparks.

Green imp/rat (Clever monster)
A monster inspired by another one from Knytt Stories (highly recommended and free)
http://www.youtube.com/watch?v=YpnGL3ggGFk (around 4:30)
They would advance at you normally, but would jump EXACTLY when you do. Otherwise they would never jump. Could be quite difficult in many circumstances, yet predictable and fair.

SAM site (Anti-Air turret)
"There shall be no jumping !" - a loose quote from the 3D game from 1983.
SAM sites would be pop-up turrets that are normally harmless. They would only activate for a short time when player jumps. Then they would fire at player. It doesn't necessarily have to be a homing projectile, just something sufficiently dangerous.

Squishy (monster)
Most of the time a quite tough monster. However, it would die easily from jumping on it. In fact, a single jump would be enough. They would still damage player if approached from any other direction.

Apple tweak (change)
It would be interesting if apples were worth 2x as much points if they were picked up before they fall to the ground. Anyone who has ever harvested apples knows they shouldn't be thrown around. A bruised apple will start to rot more quickly. Apples that spawn already on the ground shouldn't be affected.
This is not meant for realism, however. It would make the game more challenging for those who seek maximum score. Alternatively, there could be a variety of score pickup that is completely destroyed if it falls to the ground. For example - ice cream.