First off, what mechanisms are people referring to when they say that THW games are designed for solo games? Let's look at a popular THW game: NUTS!. NUTS! is a set of miniatures rules for WW II skirmish gaming. There are two primary mechanisms that make NUTS! suitable for solo or cooperative gaming: the reaction system, and the use of a random, semi-programmed enemy side.
A Randomized Opponent
Looking at the second item first, a random, semi-programmed opponent represents the strategic, of a sort. Who you are fighting, where they are located, and what their objectives are is all covered under this broad topic. NUTS! represents the strategic in two ways: Possible Enemy Forces, or PEFs; and Enemy Activity Level or EAL.
The scenario indicates the number of PEFs that should be placed at the start, and typically also indicates where these PEFs should be placed. Each turn PEFs move randomly and may possibly split into other PEFs, which in turn move on their own. PEFs are removed once they are spotted; they either turn out to be nothing or are actual enemy forces. As PEFs can split, this gives the player the incentive to scout out the enemy. An enemy force cannot split into two, only a PEF can. When a PEF turns out to be an enemy force, the reinforcement table (see below) is consulted to determine the exact force. The difference, however, is that the enemy starts where it was spotted, not on a board edge like a reinforcement.
The EAL determines when and if the enemy receives reinforcements. Unlike a traditional game, where a player typically knows how many points he has to spend, and then can spend points to choose his forces, or is given an order of battle specifying the units available, in NUTS! a player gaming solo typically starts with a set force reinforced at random, fighting unknown forces, reinforced at random. The EAL (a numeric value) gives you a sense of how many enemy are in the area, and thus how likely enemy reinforcements will show up, but generally a table and die roll determine what actually shows. (Well that and your collection of figures!)
The basic mechanism for reinforcements is that when the activation die roll (a form of initiative) comes up a '7' on any given turn, both the player and the non-player opponent roll for reinforcements. If the roll indicates reinforcements, a second roll against a table indicates the exact reinforcement gained. A third roll against a table indicates where the reinforcement arrives (generally a table edge).
With enemy forces on the board, dice are rolled for each separate force and a table is consulted to determine how it reacts to your forces in the vicinity (primarily the ones that spotted it). The good thing about these charts is that it takes into account that there may be more than one maneuver group that can take action against you.
As a scenario designer, this method gives you a different set of tasks to complete. Rather than defining points for purchasing forces (as with Flames of War), a percentage of troops to put in reserve as reinforcements (as with Flames of War missions) or developing a reinforcement schedule, or even coming up with a detailed order of battle (as with I Ain't Been Shot Mum), you determine the number of starting PEFs, their locations, the EAL, and design some appropriate reinforcement tables to reflect the forces available.
By the way, the player gets random reinforcements too, by the scenario defining a Support Level (SL), which is used exactly like the EAL, and reinforcement tables for your additional forces.
The Reaction System
Whereas the randomized opponent represented the strategic (who, what, where, and when), the reaction system represents the tactical side (or the how). Basically the reaction system is simple; it is a set of triggering conditions and responses. The player takes an action – in solo play it might be for either one of the player's forces or for the enemy forces – a set of rules are checked to see if a condition is triggered, and if so, dice are rolled to determine the response. What makes it more interesting is that the response itself could be a triggering condition, thereby forcing another response, and so on.
When describing the system and example always best illustrates the concept. A German soldier moves out of cover and crosses a street to another building. A Soviet soldier can now draw line of sight to the German (a triggering condition) and rolls to see how he reacts. Let's assume that the reaction is that the Soviet soldier fires at the German as he crosses the road. The hit misses, but being fired upon is itself a triggering condition, so the German reacts to that. Their response in turn might be to fire back. Assume he gets a lucky hit, killing the Soviet. That in turn is a triggering condition for any other Soviet soldier nearby who witnesses the death. They react, fail, and run away (but out of line of sight from any enemy).
Note that many other skirmish systems could have replicated this sequence.
- German soldier takes a Move and Fire action, even though he has no targets in sight.
- Soviet soldier, who was on overwatch on the street, takes the shot, but misses.
- The German soldier, now that the Soviet soldier has revealed his position takes his Fire action after his interrupted move and scores a kill.
- The Soviets take a morale check for losses and fail.
In many games, such as ones where you play the Division Commander, the rules author tells you that worrying about the formations of companies, or even battalions, or a myriad of other details, is beneath their purview; this is the concern of the Company or Battalion Commander. THW takes it to a whole new level by abstracting away details of the soldiers themselves. You, as the force commander, do not worry about going on overwatch, or which area is covered; you simply place the figure in a position with good visibility and facing the right way (you have a 180º fire arc, so that is not really difficult) and he is on overwatch if the triggering condition occurs and the dice indicate when the figure reacts.
An interesting point is that the reaction system does not mean the player loses total control; it does not create a self-running game. The trigger always requires a conscious action on the part of the player. That may lead to responses, which are in turn triggering actions, creating a linked chain of triggers and responses, but what starts it all is an action dictated by the player, which comes from making a choice.
I bring that point up because it is these choices that we players make that are the hardest to replicate as being a choice made by some other intelligent being, when no one else is really there. Put another way, the reaction system doesn't solve our hardest problem as solo gamers: how to determine which of the many choices open to us we should select for our opponent.
I'll try and do a game using the THW reaction system – both a mass combat system like Rally Round the King and a skirmish system like NUTS! – so I can develop this line of thought more.