Shields

Shields absorb or reduce applicable weapon damage. The installed shield Mark determines capacity, charging speed, operating cost, and resistance to impacts. Shield state records whether the field is down, raised, or damaged; a separate signed value stores its charge. Shield command covers the player's UP and DOWN actions and their restrictions.

Charging and flux use

For ordinary shield Mark M, the capacity and charging formulas are:

maximum charge       = 40 + (10 * M)
charge added/update  = 3 * M
flux used/update     = 100 * M

A raised shield is processed once per main ship-state update, normally every six seconds. It consumes the operating cost on every such update, even after reaching full charge. Starting from zero, representative values are:

Shield	Maximum charge	Charge/update	Updates to full	Approximate time	Flux/update
Mark-1	50	3	17	102 seconds	100
Mark-5	90	15	6	36 seconds	500
Mark-10	140	30	5	30 seconds	1,000
Mark-19	230	57	5	30 seconds	1,900

The displayed percentage is current charge divided by maximum charge. A normal charging update caps the value at the maximum, so the final update may add less than the nominal amount. Lowering an undamaged shield preserves its stored charge; raising it again can provide full protection immediately if the bank was already full. A power failure that automatically lowers the field, unlike a deliberate SHIELD DOWN, resets the bank to zero.

Classic 3.2e lets an already raised shield pass its periodic power check with 200 or more flux, while the SHIELD UP command requires more than 200. Neither fixed threshold covers a Mark above 2: a Mark-10 shield costs 1,000 flux per update, for example. The general ship update runs its flux-pod check before the shield step, so an available pod can refill a low pile; without a pod, a pile of 201 can pass the shield check and then become -799 after the Mark-10 cost. See Classic bug: Flux subtraction underflow and the command's initial power check.

ge-next checks the actual 100 * Mark cost before raising a shield and on each operating update, loading a pod if needed and available. If power cannot be supplied on an update, it lowers the shield and clears its charge instead of letting the pile become negative.

Protection and damage

A raised shield uses the shielded-damage path for applicable attacks. It can offer protection before reaching full charge, but the smaller bank is easier to deplete. A standard phaser hit is deflected completely: it cannot pass hull damage through a raised shield, even when the shield is not fully charged or impact damages the shield system. Torpedoes and missiles can also be fully deflected, while mines, ion cannons, and self-destruct blasts can still transmit reduced hull damage. These attacks do not all calculate their incoming strength the same way, but applicable impacts use the same shield-charge routine described below.

Charge loss and phaser magnitude

The magnitude shown to a shielded defender after a phaser hit is the incoming hit strength before shield absorption. It is not hull damage or a direct count of shield units lost. The initial charge loss for a hit strength D against a shield of Mark M is:

initial charge loss = floor(max(0, 80 - 4 * M) * D / 100)

For a magnitude-20 phaser hit against fully charged Mark-10 shields, the resistance factor is 80 - 4 * 10 = 40 and the initial loss is floor(40 * 20 / 100) = 8 shield units, not 20. A Mark-10 shield's full bank holds 40 + 10 * 10 = 140 units, so it falls to 132. REPORT SYSTEMS shows this as 94% charge after integer truncation. At Mark-1 the resistance factor is 76; at Mark-19 it is 4. A higher Mark therefore provides both a larger bank and less charge loss for the same hit strength.

The calculation truncates fractional shield-unit loss. A weak phaser contact can be completely deflected without reducing the integer-valued bank. Classic does not report a shielded phaser hit if its calculated strength truncates below 1. ge-next can report such a positive contact as magnitude <1, with no charge loss. See Phasers for how the incoming phaser strength and hit messages are determined.

Depletion and repair

After subtracting the initial loss, the shield-hit routine checks the remaining bank. If it is below the minimum raised-charge threshold but still above 2, the shield is knocked down. If it reaches 2 or less, the shield becomes damaged and another three times the initial loss is subtracted from its internal charge. Thus the final charge after a damaging hit can be negative, and the shield must be repaired before it can be raised again.

Automatic Damage Control adds the shield Mark to that negative charge on each ship-state update. Once the charge rises above zero, the system changes to down with zero charge. Classic and ge-next prior to 0.3.3 permit a command sequence that bypasses this repair state (Classic bug: SHIELD DOWN bypasses shield repair).

The installed Mark, shield state, and, when raised, charge percentage are visible in REPORT SYSTEMS. The ship class limits which Marks can be installed; class tables and shield prices are configurable. Buying replacement shields did not reset the old charge in classic or early ge-next, allowing an overcharged lower-Mark shield; ge-next 0.3.3 corrected this (Classic bug: Replacement systems retain old charge).

Shield damage in this section means depletion or damage to the shield system, not damage to the ship's hull. For the broader damage states and repair options, see Hull damage and Maintenance.

Firing through one's own shields

A ship cannot fire phasers, torpedoes, or missiles through its own raised shields. For an accepted shot, the game lowers the field and does not raise it afterward; stored charge remains, so the player can raise it manually without charging from zero. Mines, zippers, jammers, and decoys can be deployed without lowering shields.

Classic lowers shields early in its torpedo and missile command paths. Even a failed attempt, such as no ammunition or a failed lock, can therefore leave them down. Its apparent attempt to raise them after a failed command tests a status already changed by the earlier lowering and does not restore the field. ge-next 0.3.2 moved this lowering to the successful torpedo and missile launch paths. A valid phaser shot lowers shields even if it hits no target. An attempt to fire inside the neutral zone also lowers shields before the Enforcer Planet blocks the shot. See the individual phaser, torpedo, and missile command pages for those paths.

SYS-assigned shield Marks

The normal purchase limit is Mark-19. In classic GE, SYS SHIELDTYPE 20 can assign an otherwise unavailable Mark-20 shield. When raised and charged, it loses no charge through shieldhit() because its resistance factor is 80 - 4 * 20 = 0. Classic also exempts it from normal shield flux consumption and random system damage. This makes it effectively immune to ordinary phaser wear, not universally invincible: attacks that pass damage through raised shields can still hurt the hull, and firing or insufficient flux can lower the shield.

ge-next removed the special Mark-20 cases, not the ability to set the value with SYS. A SYS-assigned Mark-20 shield still has a zero charge-loss factor under the ordinary formula, but it now uses flux and follows the normal repair and system-damage rules. SYS SHIELDTYPE can also set Marks above 20. These remain outside the supported purchase range: the charge-loss factor is clamped at zero while other formulas continue to use the assigned Mark, and such values have not been fully tested for overflow or other edge cases. See SYS-assigned phasers for the corresponding weapon behavior.