Chapter 10: Core Mechanics Definition of Core Mechanics: • The rules of the game • How the player interacts with the rules • Monopoly example o Game ships with 3 pages of rules, but that would not actually be enough because you need: The prices of property Community and chance cards Rent collected from each property Layout of the board • Define rules by data and algorithms • Eventually the CMs should be so well documented that programmers could grab the documentation and have everything they need. • Interesting fact: The CMs and the game engine relationship is very close, because the CMs specify how the game engine behaves. Functions of Core Mechanics VIDEO 1 (READ DESCRIPTION FOR EACH OF THE FOLLOWING) • Operate the internal economy of game: o The core mechanics specify how the game or the player creates, distributes and uses up the goods on which the game bases its economy. o Borderlands: Randomly places ammo, weapons, grenades, and weapons in different places. Buying, selling trading occurs at vending machines. • Present Active challenges o Halo Reach: Game type Rocket race, kind of like capture the hill on crack. Hill is moved randomly, first one to make it gets a point. CMs show where the hill is to all players by an arrow.
• Accept player actions & Transmit triggers to the storytelling engine o Mass effect: You choose what to say by a wheel. Can have good or bad repercussions. Can unlock different parts of the story, or can advance the story. • Detect victory or loss o Halo reach: Detects and lets the player much more things then victory or loss. Headhunter gametype. Kill someone, collect their skull, bring to a hill. Player with most skulls at end of time limit, or if player reaches max. Collect several skulls people might aim for you because you number of skulls is displayed, so they may steal yours. • Operate the ai o Splinter cell: Last known position mechanic. AI is smart and works together to search rooms and such. • Switch the game from mode to mode o Starcraft: A lot of different modes available to you. Real Time vs Turn Based CMs work different ways for both. Turn Based Games: Wait for the player to do something then calculate the result and effects with CMs. There might be computations going on in between turns, but the AI opponents will still do moves based on turns. Real Time: Core mechanics are always implementing even if the player does nothing. AI will walk around, simulations will continue. Video 2 Total War has both of these, so here is a video. CMs and Level Design When a game loads a level, each level has its own type, winning conditions, timing, and sequence of challenges that appear. CMs specify how the different challenges actually work but not what levels they will appear in. Basically the CMs provide the level designers building blocks.
Picture 1 Important Core Mechanics Concepts The following is needed to proper document CMs. • • • •
Resources Entities Attributes Mechanics
Begin playing Video 2 • Resources o Type of object that the game can move or exchange. Game handles this by numeric quantities and arithmetic operations o Marbles can be a resource in your game if the player can pick them up trade them and put them down again. o The CMs define the process of how the game creates, uses, trades, and destroys resources o Some games often treat nonphysical concepts to be resources such as: Popularity o Part of creating resources is quantifying the unquantifiable. Like for example resistance to poison Picture 2 • Entities o An instance of a resource or the state of some element of the game world. o 3 different kinds of entities Simple entity • Can be described by one state or by a single numerical number (a single attribute) Compound entities • More then one data value to describe itself (more then one attribute) Unique entities • Only one entity of that particular type.
o • Mechanics o How the game world and everything in it works Relationships between entities Events and processes that take place Conditions that trigger events and processes o Relationships Among Entities If the value of one entity depends upon the value or state of one or more other entities, you need to specify the relationship between the entities involved. o Events and Processes When describing these, you state that something happens: a change occurs among or to the entities specified by the mechanics Event: Specific change that happens once when triggered by a condition • Skulls to hill points Process: Refers to a sequence of activities that once initiated continues until stopped. A player action or other game event starts a process that runs until something stops it. • You may have order: Socks and then shoes • Lots of examples of these o Like Arming a bomb o Conditions Conditions define when an event or process occurs (starts or stops) Different programming statements • “If (condition) then (execute an event or start or stop a process)” • “When (condition) take action to (execute an event or start or stop a process)” • “Continue (a process) until (condition)” • Used for win loss conditions o Entities with their own mechanics Some mechanics define the behavior of only one type of entity and nothing else in the game. Street light
• No equation, it consists of symbols • Numeric and Symbolic Relationships: o Interactivity between entities o Numeric: In a sports game, you could figure out the probability of injury between 2 players who collide, depending on weight, height, speed etc… Gun damage vs Health Points o Symbolic Relationships: Ruse example used, units get bonuses depending on state of area Streetlights and the AI. AI reacts differently for each state of the streetlight. o You may combine the two Racing game, changing gears • You have different ratios for the gears which take part of much bigger equations for the performance of the vehicle Fuel could be another example • When you are out of fuel and entity shows up on the screen. The Internal Economy An economy is a system in which resources and entities are produced, consumed and exchanged in quantifiable amounts. A ton of examples of these are available. A game designer spends a lot of time designing this part of the game, the more complex it is, the more time that needs to be spent on it. • Sources o If a resource or entity can come into the game, the mechanic by which it arrives is a called a source Production rate needs to be defined. Sources often produce resources automatically. In a first person shooter enemies might spawn on the map from a certain point, this is also considered a source. (Ammo and weapons could also be considered in this) Sources can be limited or unlimited
• Drains o A mechanic that determines the consumption of resources o In a first person shooter, shooting drains your ammunition, taking damage drains your health. o When creating a game drains must be explained, since resources are usually important we have to make sure an explanation was given. o In starcraft building an army is a type of drain • Converters o A converter is a mechanic that turns one or more resources into another type of resource. o Now, don’t confuse a drain with a converter. A drain in starcraft could be researching upgrades, or making defense cannons. The converter would be building your army • Traders o Traders take one item and change the ownership of that item. Maybe even allowing a different player to have ownership of the item. o Just like the borderlands example with the vending machines. • Production Mechanisms o Mechanics that bring resources into the player’s hands. o The harvesters in Starcraft are an example of a production mechanism Play Video 3 • Tangible and Intangible Resources o Tangible Resources that take a certain physical amount of space. In a FPS ammo is tangible Resident evil with ammo o Intangible If a resource has no physical space and does not need to be transported it is intangible. In Starcraft once the probe/scv/drone/worker makes it to the main base with the crystal it is no longer tangible • Feedback Loops, Mutual Dependencies, and Deadlocks o Feedback Loops
This one is a little tricky to describe, you will need resources to make more resources. The example I have for this is RUSE again, you make money by making supply depots, once you have enough money from those you can make an admin building, which makes money based on time. If my supply depots run out of money, and they destroy my admin buildings, I will be in “Deadlock”. This locks up that economy o Mutual Dependencies is when two mechanisms need each other’s output to function. o One last thing about “Deadlock”, the game recommends, programming ways to get out of Deadlock, in ruse’s case, the main base, aka headquarters, makes about the same as an admin building • Static and Dynamic Equilibrium o Picture 3 o Picture 4 Core Mechanics and Gameplay • So far we have described the core mechanics as a system but we need to emphasize a little more on the role of the player. As we discussed the core mechanics allow challenges to be detected and completed. So lets discuss the player. Play Video 4 o Passive Challenges This type of challenge does not require creating an entity to present the challenge to the player. For example a wall, the player might have a mechanic to climb but the wall itself is static. If the level designers need to detect if a passive challenge has been completed, they could simply detect the coordinates of the player, this doesn’t require any special mechanics. This is easy for the level designers to implement o Active Challenges
If you want to setup a complex challenge like a puzzle, like a puzzle to unlock a door, you must supply the level designers with: • The necessary entities and mechanics • Allow the player to interact with it • Detect when the puzzle has reached its solution Examples: • Enemies that need to be defeated o Mechanics define how the AI works o These mechanics can be used different ways to create different level designs • Starcraft campaign mode uses the same units multiple times but will still create different objectives and scenarios for a lot of the missions. o Player Actions Trigger Mechanics When you design the CMs you must specify a mechanic for each action, either initiate or start or stop a process. In a first person shooter, crouching, shooting, jumping, running, etc. o Actions Accompanied By Data Same kind of thing except along with creating a mechanic you must create an entity. The amount that a mouse was moved in a game Core Mechanics Design • Goals of Core Mechanics Design: o Strive for simplicity and elegance Simple rules are the easiest for new players to understand, and gives a much wider appeal o Look For Patterns, Then Generalize Recognize patterns instead of documenting dozens of individual cases Suppose you decide that swamp leeches really belong in water and that a swamp leech should lose 10 points of health for every minute that it’s out of the water.
o
o
o
o o
Later, you decide that a salamander should lose 5 points of health for every minute that it’s out of fire. Instead of coming up for a mechanic for each creature explain a general case only once for all environmental creatures. Don’t try to get everything perfect on paper If you try to get everything on paper you will never finish It is more important to be clear and precise in your documentation Find the right level of detail Not enough details, programmers might assume things and programming mistakes and errors will show up. But this will allow the programming stage to be fast To much detail could take too long. Revisit Your Earlier Design Work To begin designing the CMs remember to watch for the following: What is the player going to do? Your flowboard of the game’s structure Your List of gamplay modes and your plans for them The general outline of the story you want to tell The names of any characters Your General plans for each level in the game The progression of the levels Any victory or loss conditions Any non-‐gameplay actions List Your Entities and Resources Add the Mechanics Think about you resources Study Your Entities Analyze Challenges and Actions Look for global Mechanics
• Random Numbers and the Gaussian Curve A lot of games use random numbers, for example the shots from a gun can have a certain accuracy. Say .8, if we generate a number between 0 and 1 we can compare that number and if it is below .8 we can say it is a hit. o Pseudo-‐ Random Numbers Random number generator algorithms take in something called a seed. Then the algorithm creates a random number. The only issue is that if you don’t change the seed you will end up with the same random number. Not really fun, especially for some kind of game that includes a dice roll, but it is pretty good for testing. (Counter Strike for example) o Monte Carlo Simulation Sometimes it is hard to test a system when there are many different inputs that could occur. So we do something called a Monte Carlo simulation, this just means that we test a system with a bunch of inputs and record the outputs in a file. In a game like FIFA manager, you don’t have to sit through every game, games are simulated, and probability is calculated for each game. From the output file you should notice stronger teams beating weaker teams. But every now and then a weaker team should win. This is normal. o Uniform Distribution The chance of getting one number is equal to the chance of any other number. Like a dice roll. o Nonuniform Distribution Difference probability for each randomly generated number. Like 2 die being rolled, chance of rolling a 12 is different then rolling a 6. o Gaussian Curve
Appears very often in nature, it is just like a 2 die being rolled.
