Overflow is a technology which makes blocks which normally generate propulsion to generate drag instead, by setting their power values to large numbers.
In computing, numbers have finite minimum and maximum values due to hardware limitations. 'Overflow' is when a number (i.e. a variable) is set to something outside of that range. Depending on the storage format of the number, it will do different things. Some cap out, some wrap around, and some set themselves to special values.
Using NoBounds, you can set block power values (e.g. water cannon power) to any value - including values where variables start overflowing.
The physics engine does not define anything which is intended to deal with this, so it does unintended stuff instead. Thankfully, for anything dealing with force, the behaviour is consistent and useful. Instead of propulsive force, the block will generate extreme drag.
The threshold for overflow behaviour is at most 1 x 10²¹. No lower bound has been properly established.
Overflow is a simple method of high-power Recoil Suppression - a handful of overflow water cannons can effectively dampen recoil from 100x power cannons with minimal weight and parts.
(In a similar vein, it is (in theory) useful for armour; given enough travel distance, an armour plate augmented with overflow blocks can stop high-power kinetic weaponry.)
Another major use of overflow is on hovering vehicles to stop drifting and smooth movement. This is particularly important at slow speeds where aerodynamics are not an effective way of dealing with these problems. It is possible to use enough overflow blocks that the force of gravity is reduced to insignificance (although it will never be perfect, since they provide no upward thrust on their own).
Its properties also make it a good stand-in for a parachute.
A lesser-known overflow block is the vacuum - it applies the overflow effect to anything in its firing range (which is quite substantial). This makes it useful for immobilising vehicles (particularly ballast tanks) and tearing apart aircraft as well as all of the applications the thruster blocks are used for.
Advantages and Disadvantages Edit
For recoil suppression and armour, overflow is highly effective and very simple (as detailed in the last section), which makes it a highly attractive option.
However, it has one major downside - the machine cannot move fast (or at all) while the overflow system is turned on. This makes it very difficult to use on aircraft and any tank which can move faster than walking speed, and makes the machine a sitting duck in combat. This is less of a problem for stationary or slow-moving installations.