Skaphander: Der Auftrag/Gameplay

User interface
The cockpit displays along the bottom of the screen are divided into six sections. From left to right:
 * Score: Score does not affect anything, but it is useful for tracking your progress through a level.  (In fact, some actions can be repeated indefinitely to increase the score until it overflows.)
 * Compass: The compass shows the Skaphander's current heading and is useful for orienting yourself with respect to the HUD map (which is always shown with north at the top). The compass letters are from German, so "east" is shown as "O", for "Osten".
 * Inventory: The inventory screen shows what tools, if any, the Skaphander has in its inventory.
 * Vehicle Status: The vehicle status display shows the condition of the Skaphander, mainly whether or not a protector is equipped, but the vehicle's wireframe also does change orange and then red as the vehicle takes damage, so it can be useful to keep an eye on its color.
 * Data: Data represents the vehicle's health (see below). It ranges from 0 to 400.
 * Energy: Energy represents the vehicle's fuel/ammo (see below). It ranges from 0 to 300.

The main screen shows the view from the Skaphander. Overlaid on that view are the currently selected weapon(s), a targeting reticle if the weapon(s) can be aimed, and the HUD map if it is enabled.

Resources
The Skaphander relies on two resources:
 * Data: The game's equivalent to health, Skaphander's data protects Victor's brain from destructive feedback through the HMD—if it reaches zero, then Victor suffers brain damage, and the game ends. The Skaphander begins a level with 300 data and can attain a maximum of 400.  An auditory warning plays continually if the Skaphander's data falls below 50.  Data is lost to impact with enemies or terrain (even driving over an uneven floor too fast can damage the Skaphander), to enemy weapons, or to contact with corrosive Matma.  Data is regained by collecting data refreshes (see the section below) or by connecting to a repair station.
 * Energy: The game's combined fuel and ammo resource, Skaphander's energy allows it to fire reusable weapons and to move forward or backward—if it reaches zero, then the Skaphander will still be able to turn and strafe, but forward and backward movement will be extremely slow, and reusable weapons will not fire. The Skaphander begins a level with 300 energy, which is the maximum it can attain.  An auditory warning plays continually if the Skaphander's energy falls below 50.  Energy is slowly consumed by moving forward or backward and more rapidly consumed by firing reusable weapons, with heavier weapons requiring more per shot.  Energy is regained by collecting recharges (see the section below) or by connecting to a charging station.

Resource items
The Skaphander can renew its data or energy by collecting resource items:
 * Data Refreshes (Spanners/Wrenches): Data refreshes are shown on-screen as gray or blue spanners/wrenches. Driving over a data refresh will increase the Skaphander's data by 25 (6.25%) up to its maximum of 400.
 * Energy Recharges (Batteries): Recharges are shown on-screen as pink battery cells. Driving over a recharge will increase the Skaphander's energy by 25 (8.33%) up to its maximum of 300.
 * Sixpacks (Batteries): Some recharges come in sixpacks, which must be collected all-or-nothing. Driving over a sixpack will increase the Skaphander's energy by 150 (50%) up to its maximum of 300.

(Ranged weapons also add 200 energy when picked up, so a ranged weapon that has already been collected can still be valuable as a large reserve of energy.)

A big part of Skaphander strategy is leaving resources in place for when they will be needed later, so it is important to avoid collecting these items when their benefits would be lost to the Skaphander's resource caps. As a corollary, it is usually better to secure an area before topping off data or energy; the items might be worth more after spending resources on a fight.

Weapons
The Skaphander can equip a variety of reusable energy weapons for use against viruses:
 * Debuggers: Debuggers are reusable light guns with low recoil that, unlike all other weapons, can be dual-mounted. Each debugger consumes 1 energy per shot to deal up to 10 damage (depending on the accuracy and range of the shot); a debugger's maximum rate of fire is two shots per second. Because debuggers are side-mounted, a single debugger causes asymmetric recoil, the direction depending on which side it is mounted on (normally the left). Besides doing damage, debugger fire can also activate switches, activate pillars, or detonate explosives remotely. For such utility use, it is better to switch to a single-mount configuration to conserve energy.
 * Double Eraser: The double eraser is a heavy gun with stronger recoil. It consumes 6 energy per shot to deal 30 damage (depending accuracy and range) and can fire four shots per second. Besides doing damage, debugger fire can also activate switches, activate pillars, or detonate explosives remotely, but it is less suited to these tasks than the debugger.
 * Interrupter: The interrupter is an even heavier artillery weapon, similar to a ranged version of breakpoints (described below). It consumes 20 energy per shot to fire an exploding projectile that does 100 damage at its center and slightly less as splash damage; because of the large blast radius it can be used to destroy multiple viruses at once or aimed at walls to damage enemies around corners. On the other hand, an interrupter blast is indiscriminate and can harm the Skaphander itself, making it poorly suited for battle in tight spaces, and the recoil is so bad that the weapon is virtually unaimable when its pitch is not locked, so it fares poorly against enemies not at eye level.

The Skaphander can also deploy single-use breakpoints:
 * Breakpoints: Breakpoints are non-reusable proximity bombs shaped like underwater mines that audibly tick when armed. Using the fire key/button while a breakpoint is selected will toss it a short ways (about the length of its blast radius) onto the ground in front of the Skaphander, and it will detonate for 100 points of damage when any virus enters its blast radius or when it is shot with a debugger or interrupter. Breakpoints are indiscriminate and can harm the Skaphander itself. The Skaphander can only carry up to five breakpoints at a time, and uncollectable breakpoints act as obstacles, so sometimes it is necessary to drop one breakpoint in order to collect another in the way.

And the Skaphander can carry one mêlée weapon that can damage the environment itself:
 * Separator: Being a side-mounted saw, sustained use of the separator can cut through weak barriers (like chain-link fences) to open up new passageways. It does not meaningfully damage viruses though.

Weapon pitch
Weapons are normally mounted at a fixed angle on the Skaphander, but they can be unlocked by pressing PgUp/PgDn (or, equivalently, Num 9/Num 3) to adjust their pitch up or down. (This is also useful just for peering over ledges or up shafts.) However, while unlocked, the weapons swing much more freely, and so it is difficult to maintain aim when the suspension rocks or a shot causes recoil. The Skaphander will also automatically relock weapons in their default position after a few seconds of no pitch adjustments, so to maintain a nonstandard pitch for any length of time the player must periodically tab these keys to make fine adjustments.

Protector
A protector is additional armor that absorbs damage from Matma. It is shown as a white overlay on the vehicle status indicator. A protector has limited durability and, critically, there is no way to see how much damage it can still take before it fails.

Sublight scanner
The sublight scanner allows the Skaphander to see and interact with hidden items at the cost of color vision; everything appears as some shade of red while the scanner is active. (Because the red coloring is the same effect used when under Matma, there is a game bug that can be triggered by toggling the scanner under Matma where these visual effects are reversed, and the scanner has to be active to see in color.)

Tools
The Skaphander can carry various level-specific tools, which are shown on the inventory display. Tools let Victor interact (using the "manipulate" command) with corresponding switch-like objects that otherwise would be unreponsive.

Bugs
Besides viruses, which actively resist Victor's incursion, the network is also plagued by passive bugs, which are represented on screen as silver (minor) or gold (major) beetles. The Skaphander can squash bugs by driving over them (similar to how items are collected). Starting in the level "Rael", some bugs are invisible and can only be squashed with the sublight scanner active—without it on the bugs just act like invisible obstacles.

Spiked viruses
A spiked virus is a common, low-level enemy that appears as a floating spiky gray ball and flashes red when aggravated. (One contemporary review jokingly called them "Christbaumschmucke", or Christmas-tree ornaments.) Spiked viruses have 40 health and no ranged attacks but can still do damage by ramming the Skaphander with their spikes (which hit for 10 damage) and by pushing it into hazards or off ledges. Normally they stand guard at ambush points and do not move until they detect the Skaphander. They particularly like to surprise Victor from above or below, but their vertical speed cap is much lower than their horizontal speed cap, so sometimes they get themselves caught for a bit on ledges or overhangs.

Spiked viruses have a number of tactics that they might employ:
 * When far away with a good line of sight and no incoming fire, they simply charge the Skaphander, easily matching its maximum speed.
 * When far away with poor line-of-sight to the Skaphander, they will look for corners of walls to hide behind in ambush. They always converge to their target's altitude, so once they engage in a fight they are usually stuck on the same plane as the player.
 * When being shot at, they will make rapid lateral movements in hopes of outpacing the Skaphander's turn rate.
 * When close by, they will attempt to dart behind the Skaphander and attack it from behind, again exploiting its slow turn rate.

Blobs
A blob is a late-game mêlée virus that appears like a pulsating, primary-colored bouncy ball. It sacrifices almost all of the spiked virus's maneuverability in exchange for more health (100–300, depending on the variety) and harder hits (50–100 damage, depending on the variety). Their behavior is not particularly interesting, as they mostly just approach, soak up damage, and ram the player, but they can be a serious impediment when blocking hallways or doors or on levels where energy is hard to come by.

Barnacles
A barnacle—or perhaps a pair of barnacles—is a spherical virus that splits itself into two hemispherical suction cups. It has 100 health, but can do no damage. Instead, its real danger is that when it touches the Skaphander, it can attach itself to the cockpit glass, obscuring the player's view until the end of the level. Like blobs, barnacles do not feature sophisticated tactics, relying instead on their high health and undesirable attack.

Clamps
Clamps are floating vises that can open up their pincers to reveal two machine guns. They are extremely common. Clamps have 90 health, and their machine guns can do up to 20 damage apiece per shot (depending on accuracy) at a maximum of four shots per second. Taking damage spins the viruses around, interrupting their fire as they can only fire forward. Like spiked viruses, clamps can also ram the Skaphander either to do direct damage or to push it into environmental hazards. Clamps normally have patrol routes that they follow until they become aware of the Skaphander. They move slower than spiked viruses horizontally, but can change altitude more quickly.

Clamps also have several tactics that they may use:
 * In normal circumstances they will charge the player, relying on their high health and damage output to ensure their survival and eschewing lateral movement in favor of maintaining gunfire. They may approach obliquely when still too far away to target the Skaphander.
 * If they are taking damage, especially in close quarters, they may try to make short lateral movements before charging again in order to avoid the player's fire.
 * If they are heavily damaged (causing them to appear not just burnt, but with "corrupted" graphics), they will flee to heal themselves.

Unlike in the 1997 game's opening cutscene, in the 1995 game these viruses cannot grip the Skaphander.

Turrets
Looking like a cross between a top and a fishing bobber, a turret is an extremely strong ranged virus. Turrets boast 180 health and can fire homing artillery for 50 damage per shot and the longest range in the game, though this power is mitigated by their slow rate of fire, the fact that they cannot fire while taking damage, and the fact that the artillery shells can be shot down. Turrets like both to float over depressions or pits where they can duck down and to take the high ground and fire from above. Either way, they often force the player to rely on pitch controls (and the associated recoil issues) to score hits.

Special viruses
There are also a number of one-time or otherwise special enemies:


 * The Floating Face (perhaps the Michaelangelo [sic] virus itself—the game is unclear on that point): A floating face appears beyond a Matma pool in the first level, "Michelangelo". It deals no damage itself but it also ignores most attacks, only succumbing to very short-range projectile weapons fire. Defeating it causes the Matma pool to freeze.
 * The Blob Spawner: A late-game virus, the blob spawner features a whopping 700 health and can slowly spawn 100-health blobs to defend itself.

Steps, ledges, and pits
Besides damage from enemies, the Skaphander also takes damage if driven recklessly. Because of its armor, impacts with walls do not hurt it, but it is instead the vehicle's underside that is vulnerable. In particular, where the terrain changes in steps, the Skaphander can be damaged by driving (or being pushed by an enemy) over those steps more quickly than its suspension can handle, and more serious falls will hurt it even more. There are four common categories of changes in ground level:


 * 1) A small step is the most common fixed change in ground level, one that's the same size as the depression in the middle of the game's first room, the chapel in the "Michelangelo" level, but not so thin as the red "rug" at the entrance to that room. Small steps are generally safe to drive over unless the Skaphander is somehow above its normal top speed (e.g., it is using or has recently used turbo, it is sliding on frozen data, it is being pushed by an enemy, it is bouncing off another step or wall, etc.). Descent does slightly more damage than ascent.
 * 2) A large step covers anything larger than a small step up to twice that size. Crossing one can damage the Skaphander even at normal speeds, though not if the Skaphander traverses it slowly. Again, descending a large step requires more care than ascending one.
 * 3) A ledge is an even larger change in ground level that the Skaphander cannot ascend, one that deals damage unless the Skaphander drives extremely slowly, and the drop is short. An early example would be jumping down from the ledges encircling the chapel, which at normal speed will deal about 60 damage.
 * 4) A pit is an area of ground with effectively no bottom. Driving into a pit will certainly cause the Skaphander to be destroyed unless that pit is an escape shaft, the exit to a level, also sometimes called a "transmitter" in game. Escape shafts are distinguished from ordinary pits by the Firm's two-headed-snake logo.

If the Skaphander is approaching a small or large step at speed, it is possible to brake with reverse thrust to reduce or eliminate any damage that might be taken when the vehicle crosses.

Switches and buttons
Switches are devices that the Skaphander can toggle from nearby with its manipulate action or from afar with ranged weapons fire. Their purpose varies by level, but often there is signage nearby to describe what they do when toggled. They appear as pink circles in pink squares, the upper or lower half of the circle shaded darker to indicate their state.

Buttons are variations on switches that can be pressed in the same way that switches are toggled or also by ramming. Unlike with switches, there is no way to "unpress" a button, though a button may become unpressed automatically or in response to other events. Buttons appear the same as switches except that the whole circle is shaded according to their state.

Doors
Doors between rooms are motion-sensitive and will open when the Skaphander approaches. Sometimes it is possible to end up in front of a door, but not by approaching it, in which case the Skaphander must retreat and reapproach to trigger the motion sensor.

Closed doors block both viruses' line of sight and their movement (viruses cannot trigger the motion sensor), so it is possible to lure an enemy into a room and trap it there.

However, in early demo versions of the game, closed doors did not block viruses' movement, rendering that tactic ineffective. Still, a virus would only phase through a door if it knew from earlier observation that the Skaphander must be on the other side, so, in those demo versions, a door was still useful cover to avoid aggravating an enemy in the first place.

Lifts and pillars
Lifts and pillars are terrain tiles that rise, sink, or alternate rising and sinking, normally based on the Skaphander's location, but very occasionally when triggered by switches. Most begin moving to the other end of their vertical range when the Skaphander drives onto them, when the Skaphander uses the manipulate action on them, or when they are struck by ranged weapons fire. But others feature a variety of movement rules—some move in different directions based on where the Skaphander sits on them, yet others are triggered once by switches, and still others might be enabled by switches but only respond when the Skaphander is in a certain location.

Because they are solid underneath, the Skaphander cannot end up below a lift or pillar, but some pillars rise all the way to the ceiling, so it is still possible for them to crush the vehicle with upward movement.

Like ledges, both lifts and pillars present some environmental danger to the Skaphander. Just as with any other step, driving between a left/pillar and a surface at a different height can damage the vehicle depending on its speed at the time. Worse, if the Skaphander straddles the boundary between a stable surface and a lift/pillar, the rise or fall can tip it, not only destroying vehicle's data when it contacts the ground, but possibly sending it sliding at high speed into other terrain or over a ledge. Then too, there is the possibility of being crushed against a ceiling, which can do hundreds of points of damage in an instant.

On the flip side, lifts and pillars can also be used strategically to block or relocate enemies.

Matma
Matma is a red corrosive liquid with a lava-like appearance, usually confined to pools. It acts as a "energetic defluctor", which in gameplay terms means that any contact with it damages the Skaphander continually and prevents the firing of energy weapons. It does not damage viruses.

In some levels, matma can be neutralized by freezing it, leaving behind frozen data.

Frozen data
Frozen data is a slippery, blue-and-white, ice-like surface. On its own it poses no danger, but fighting on frozen data can be difficult, and it is very easy to build up too much speed and take damage by running into steps or falling off ledges.

Stations
Stations are larger, wall-mounted repositories of data (a repair station), energy (a recharge station), or information (an info station).

When the Skaphander makes contact with a resource station by driving into it, it becomes magnetically attached, and the station slowly transfers its resource until the vehicle reaches its resource limit or the station's reserve runs dry. This makes stations useful for topping off, since they only provide what is needed, and nothing goes to waste. On the other hand, because of the magnetic attachment, the Skaphander is nearly immobile for the duration, and because of shaking from the resource transfer, aiming is also quite difficult during that time, so stations are much less useful than resource items in a fight. There are two types of resource stations:

A repair station, which contains data, looks like a vertical tube of pink liquid with two orange arrowheads pointing at it. Vents and lights appear on the sides, and blue spanner/wrench icons are shown at the top.

A recharge station, which contains energy, looks like an electrical panel with hex sockets and strain insulators, the panel being below some vents, next to some blinking lights, and flanked by two vertical tubes of blue liquid. A black lightning bolt on a yellow ground appears in the center.

In both cases, the height of the liquid in the tubes indicates the amount of resources remaining within the station. In cramped quarters, it may be necessary to pitch up to see the level in the tubes.

An info station, which looks like a PCB-mounted LED blinking red and white, works differently, providing an on-screen message related to its topic when driven into. The message is given instantaneously, with no magnetic coupling.