A squad based tabletop RPG that takes place on a rolling battlefield rather than in a room based dungeon, with AP based traversal mechanics that force the player to consider how they cross the field.


Player characters are transforming mecha. Each mecha has two modes. Vehicle and Robot mode. At the beginning of the game the player chooses a vehicle mode, which determines their basic attributes. For example A tank would be a slow but heavily armored character, while a jeep would be a fast but lightly armored character, and a hover bike would be able to cross terrain effortlessly but would have minimal attack or defence.

In order to encourage the player to utilize both modes there are certain tasks that can only be accomplished in one mode, or which may be accomplished better in one mode than the other.

For example, a tank might be able to burst through an obstacle more effectively in vehicle mode, while a jeep might be better at climbing over it in robot mode, while a jet bike would suffer no movement penalties in either mode.

One core mechanic is that the mecha's primary weapons have a debuff one mode, or only become available in one mode. This would, for example, encourage the tank player to consider if it was better to use AP to transform into their tank mode in order to gain access to a powerful ranged weapon and increased armor, or if it would be better to use their AP to fire more shots from their lighter robot weapons, or to spend AP on movement to get to cover.


How can this be justified form a lore perspective?

For a tank it's relatively easy to say that the need a stable firing platform to fire their main gun, so they need to transform in order to do it, how would you apply this to a character with a highly mobile vehicle mode without a high recoil weapon, or a character with a transport based vehicle mode (Heavy truck, etc) that has to transform in order to be able to use its primary ranged weapon?

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    $\begingroup$ You're already in fantasyland when you have transforming mecha so why do you need an explanation? $\endgroup$ Commented May 12 at 3:55
  • $\begingroup$ this going to depend on the mech and the weapon, since you admit the rules for weapons and forms are not consistant. $\endgroup$
    – John
    Commented May 12 at 12:40
  • $\begingroup$ This reminded me of Lego Alpha Team Game, if you are looking for ideas! $\endgroup$
    – IronEagle
    Commented May 12 at 22:41
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    $\begingroup$ @xLeitix : the ability to transform in the middle of the mission is mentioned in the question: "... the player to consider if it was better to use AP to transform" $\endgroup$
    – vsz
    Commented May 13 at 8:10
  • $\begingroup$ @vsz Fair enough, I see that I misread the sentence "At the beginning of the game the player chooses a vehicle mode". $\endgroup$
    – xLeitix
    Commented May 13 at 9:09

8 Answers 8


Power distribution

Transforming modes means transforming the whole way the system works. Let us say you have a tank gun in a vehicle configuration. When you transform to a mech, you are transforming you mode of movement. This requires a qay to be powered. You can argue that the gun mechanism is adapted to provide this power, making the mech lose the gun.

You can reverse this in other ways. Say a mech with rocket pods transforms into a hovercraft with a laser weapon. The laser weapon functioned as the power generator for the mech, but after transforming the hovercraft is using the previous rocket power for mobility, allowing the power plant to be used for the energy weapon.

These are just a few quick examples. There is one easier reason though. In a real battlefield there is too little reason to have something transform. You already have suspension of disbelief for the transformers, what is a few weapons added to it as well?

  • $\begingroup$ I hadn't thought of that, the mecha simply needs more power so it has less for it's lasers. $\endgroup$ Commented May 12 at 13:10

Because the Weapons can only be Zero'd or bore-sighted in one specific configuration

So, this answer, whilst it could be overcome with sufficiently precise machining of parts and fire-control computers, has a basis in real-world firearms mechanics. And depending on your combat ranges (Small errors at short range are epic misses at longer ranges) you can have a very realistic example.

In the real world, if I have a rifle, with say a picatinny rail for my scope mount - like this:

Rifle Scope and mount

I have to Zero the rifle - typically that involves first bore-sighting it (assuming it is a brand new rifle and never been zerod) - which is you put a special cartridge, with a laser in it, in the chamber - look where the laser is pointing at a specific distance and adjust the scope (the knobs on the top and side of the scope) so that the crosshairs are in-line with the laser.

Then you go to a range, and sight your rifle in by firing a series of rounds, calculating the average impact point etc.

Now - if I take my scope off, even if I have super-duper precision machined parts, I still have to re-zero my rifle.

Granted with modern optics and equipment, this may be only a few clicks of adjustment needed - but you get the picture.

There are some dove-tail scope mounts that supposedly can be taken off and on without re-zeroing, but anyways.

When you change configurations, there are so many changes to the how the mounting system is aligned with the targetting and sighting system that the weapons system is effectively unusable.

Bonus idea for a game mechanic - they can use it, but at a significant reduction in aim, to account for this.

When the configuration is changed back - although it is not a perfect re-alignment (again - could have a game mechanic where you spend an AP after changing back to re-zero the weapons system to restore accuracy) - the Sights are back on target.

  • $\begingroup$ That could definitely be an answer in a steampunk environment, but I'm not sure that it would be convincing with giant robots given that we're fast moving beyond traditional optics in our modern vehicles. $\endgroup$ Commented May 12 at 13:07
  • $\begingroup$ All projectile weapons that aren't tracking need to be zeroed. Whether that is with an optic or with a fire control computer - you need to sync where the projectile actually hits to where you think it should. $\endgroup$ Commented May 12 at 19:29
  • $\begingroup$ The weapons may not be "classic" projectile weapons, given that we're into the fantasy of transforming mech, they could be lasers (or other "aiming point = impact point" energy weapons or guided missiles, neither of which need zeroing. $\endgroup$ Commented May 13 at 7:57
  • $\begingroup$ @KerrAvon2055 - Even ranged weapons unaffected by Gravity or wind would need some form of Zeroing - that is a calibration between the actual muzzle and where the targetting system believes it is. $\endgroup$ Commented May 13 at 8:20
  • $\begingroup$ @TheDemonLord, I'm not sure how to explain forma lore perspective why the manufacturer wouldn't account for this in the transformation process. For example why a fire control computer wouldn't simply be able to compensate for the new location. $\endgroup$ Commented May 14 at 8:26
  • Certain weapons are likely to damage the vehicle in one mode, but not in the other. It could be that recoil is so bad that a stable platform is needed (tank tracks). Or they eject casings which might fall into a turbine intake and damage the engine.
  • Certain weapons can be fired in both modes, but they are unlikely to hit in one of them. Artillery which would spin a hovercraft around, but not the legged mode.
  • $\begingroup$ An example comes to mind: When transforming, certain parts are mid-hinging, making it so that a heavy recoil could break those hinges. $\endgroup$ Commented May 13 at 8:18
  • $\begingroup$ Tank tracks do not, in and of themselves, provide stability. The stability comes from the tank's wide footprint and its low center of gravity. The tracks distribute its weight so that it can "float" over soft ground rather than sinking in up to its axles the way a wheeled vehicle would do. $\endgroup$ Commented May 13 at 14:57
  • $\begingroup$ Early airplanes in WW1 had exactly that problem; they were able to shoot to the back but not to the front because that would damage the propeller. The synchronized machine gun was invented as a solution to the problem, which would send bullets forward between the rotating propeller blades. $\endgroup$ Commented May 13 at 20:20

The transformation moves the weapon

In the process of transforming to the different modes, parts get moved around. Perhaps the ideal mounting point for the weapon in one mode leaves the weapon pointing in a useless position in another. Alternatively, the mounting is only able to properly support the weapon in one mode, and in the other, it is unable to take the recoil(for things like the tank).

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    $\begingroup$ From a lore perspective, why would someone build a weapon that can't be repositioned in an effective way that keeps it functional? I'm thinking of things like Galvatron's primary weapon which becomes an arm canon, or the Macross gun pods that become assault rifles. $\endgroup$ Commented May 12 at 13:09
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    $\begingroup$ It might be that the ending position of the part the gun is mounted to ends up in such an impractical position that it's not worth trying to make it useful, eg if the autocannon of a self-propelled anti-air gun ends up in at the base of the leg. No matter how you rotate it, it's not much use in that position. Or even if it is somewhere with good firing arcs, something like the main gun of a tank needs carefully designed mountings to support the recoil, which is likely to be disrupted by transforming the whole vehicle(for the high-recoil weapons). $\endgroup$
    – Bubbles
    Commented May 13 at 1:03
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    $\begingroup$ The weapon could form an essential part of the vehicle. Let's say a Mech with a long range sniper rifle has a vehicle mode of a motorcycle. The rifle may be made of a heavy, durable material that can withstand the propellant forces required to launch a projectile the required distances, and so it also doubles as the main body of the motorcycle with wheels connected in front and back. You could still fire it, but only forwards. Or, to minimize weight, the barrel of the firearm is dual purposed to dissipate heat and exhaust generated by vehicle mode operations. $\endgroup$ Commented May 13 at 13:31

The crux of the question seems to specifically center on the case of a smaller vehicle losing access to a smaller weapon when it transforms into a tank-like form, so that is the case I will specifically address.

Dimensional Swapping

Your vehicles can transform by moving matter along another spatial dimension. This allows the vehicles to effectively change their own mass, meaning you can hide away all of the armor when you're in a lighter and more mobile form, then bring it back when switching to tank mode.

Unfortunately, maintaining access to this dimension requires that something be kept inside it at all times to serve as an anchor. Since the engine and crew are already spoken for, it's the light machine gun that needs to be stowed away during tank mode.


The actual mass of your transforming machines never changes. So, if you want extra armor, that mass needs to come from somewhere. Thankfully, super-potent nanobots are able to disassemble and reassemble your light weapons so quickly that they can be turned into armor during tank mode. As a bonus, the big gun on the tank can be turned into a more powerful engine on the mobile bike form.

These aren't very intelligent nanobots, though, so they can't be expected to repair damage or disable enemy machines.

Firing Requirements

If your vehicle can swap between a grounded mode and a hovering mode, maybe it has a weapon that requires being airborne to use. Perhaps a bomb that it relies on dropping from overhead, or an electric cannon that would ground itself if fired too close to the ground. Depending on the terrain, it's also reasonable to imagine a sniper rifle that is only accessible while hovering because it was built to fly over a treeline before shooting.

The obvious corollary is that the ground based weapon causes too much kickback to be used in the air, but maybe the ground weapon is some kind of flamethrower or gravity cannon that the hovering mode uses for lift.

Health Hazards

For the specific case of a transport needing to transform, make its primary weapon extremely dangerous to be around. A sonic cannon that would deafen anyone inside, a flamethrower that overheats the transport bay, or a gun that would cause enough kickback to damage the transport bay. It may not sound ideal, but wartime is full of haphazard inventions - all the generals care about is getting troops to the front line and then blasting things. Safety concerns can be hashed out on the front.


The hover bike's weapons are heavily integrated and have fixed aiming. The entire vehicle is used to aim the weapon, and the hover bike's mobility makes this possible. Tanks and jeeps are too cumbersome to do this effectively. Transforming into a mech orients the gun straight up (or down) making it impossible to aim.

The mech's weapons are too complicated or risky to automate and require manual steps, such as breaking open a rifle, ejecting the used shell and inserting another. This requires giant robot hands to perform the manual operations.

The tank's simple propulsion requires less energy for movement and can use that additional energy to power the big weapon.

The jeep has a fully articulated weapons, but is limited by the amount of recoil it can absorb.


A narrowed but interesting case would be the stealth characteristics, closely tied to the real world, as in this source:

exploiting the moment when the low observability of the Nighthawk was degraded by the opening of the bomb bay door.

A stealthy aircraft becomes much more visible after opening the bay doors to drop bombs or deploy other weapons. It may also take more weapons or fuel tanks on external hard points, but again this make it well visible on radar.


Frame challenge: It can't - and that doesn't matter

There are so, so many SF/F rulesets where the "fluff" of why things behave the way they do really doesn't stand up to close scrutiny.

I'm most familiar with Warhammer 40,000 which is a perfect example. The lore is very clear that all races move between solar systems (or significant areas of space anyway) in city-sized ships, and that all races have the ability to conduct orbital bombardment. Yet they all send in ground troops to fight it out on the planet's surface, instead of simply wiping out the defenders from orbit. Even when it comes to ground assaults, they're all stuck in a Napoleonic-era concept of battle where combined-arms operation simply doesn't happen. The games doesn't even give you WWI-era concepts like creeping barrage, never mind WWI-era air superiority. Compared to modern concepts of warfare with close air support and drones, it doesn't even pretend to make sense.

Does that stop anyone playing WH40K? Of course not. It's the biggest franchise in the market, and a major reason is that it's fun to play. Restrictions on what units can do are all imposed in order to make the game well-balanced, and that's what matters. The fluff to justify this is generally pretty well written (I've a lot of time for Dan Abnett in particular), but that doesn't mean it holds up to more than fairly casual scrutiny.

So invent any fluff you want. It doesn't have to particularly make sense - and after all you're talking about giant transforming robots which inherently don't make sense in the first place! You just have to state that this is how your magic giant robots work, and that's all there is to it.


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