New Gameplay Mechanics
Two main resources
Blizzard has confirmed the addition of a second collectable resource into the game - mana stones. Unlike gold, which is harvested from gold mines and is plentiful, mana stones can only be collected by killing NPC "creeps" on the map. There are a small, finite number of mana stones on any given map.
The primary use of these mana stones is to purchase and build new heroes. Blizzard's Rob Pardo mentioned that they might also be used to purchase high end upgrades for heroes and possibly all upgrades, but that detail has not yet been decided. Players will start with enough mana stones to build one hero. This basically forces players to go out and explore the map to find NPC characters to battle with so that more mana stones can be collected.
The addition of mana stones into the game design fits into Blizzard's plan that heroes should not be treated as merely super combat units. In early play testing, Pardo mentioned that it became a problem when testers would simply mass build a large unit like the Abomination to go out and fight. In response, Blizzard has weakened the fighting ability of low level heroes in order to encourage players to level them up. The mana stone requirement to buy heroes should also keep players from just substituting a lot of low end heroes for regular combat units. Resurrection of dead heroes will cost no mana stones, so recycling old heroes could be more cost effective than building a bunch of new ones.
Dwarven Riflemen, Footmen, and a Paladin against Orcish hordes
Another new game feature that Pardo demonstrated to us was the day-night cycle. Although the timing is definitely going to be tweaked a lot before the game is released, the cycle in our build lasted about 4 to 5 minutes total (day to night and back again). Why have a day/night cycle? Certain races, like the Night Elves, and the Undead, will have bonuses depending on the time of day. Some of the Night Elf warriors can "shadow meld" automatically when it's night-time. This means that as long as they remain motionless, and not attacking, they will be cloaked from view. Visually, this was represented on screen by the character models turning to a light gray transparency. However, Pardo noted that the graphics for it will probably be tweaked soon. It is unknown what type of bonuses the Undead might get during night-time operations.
How can other races combat the night-time advantage? Well the item usage we mentioned earlier might be one option. Pardo demonstrated this by taking an Arch-Mage and mass teleporting over to a neutral merchant on the map. You need a hero to buy, carry, and use special items - these include things like rings of regeneration, potions of various types (invisibility, resurrection, etc) and day/night stones. Bring a day stone with you to a Night Elf town at dusk, and instead of trying to figure out how strong their force is (because of shadow melding), just activate your day stone and turn the time to dawn. Of course, if the Night Elves have a night stone, that could present a problem...
Human Arch-mage casts blizzard - all that's left is an Orc Wolfrider. A Gyrocopter flies overhead
Yes, the forests on the map can be cleared away by your peasants. Lumber is not a resource in the game, but this ability will bring back the old "chop into the back of your enemy's base" strategy. There will also be a number of maps where gold mines and other goodies are hidden inside of forests. Peasants will also be able to pick away at rock formations and rock walls on the map. Stop hiding, cowards!
No more black shroud
Rounding out the list of notable gameplay mechanics that we noticed on our visit, the black shroud that hides the terrain in the minimap has been eliminated for multiplayer matches. The fog of war is still on by default, of course (standard for all Blizzard RTS titles), but players should no longer have to fear "not knowing a map." Pardo said that they viewed it as a problem that most players on StarCraft Battle.net seem to play just Hunters and Lost Temple. They hope that eliminating the shroud will make playing new maps less intimidating. The map selection screen before a multiplayer game launches will also show a preview of what the map looks like, which should also help the situation. We feel that this is a good move, since hiding the terrain is a rather unnecessary hindrance for multiplayer. Single player missions will still feature a black shroud, so players will have the opportunity to enjoy some exploration.