Strategy games sometimes offer extra ways to detect the enemy, beyond the standard line of sight, with radar being a classic example found in Zero-K. Radar reveals quite a bit about player interaction, but we will also have to flesh out vision itself, since the two systems complement each other. Both systems use the same underlying mechanics, which were covered last time, although the details are not strictly necessary for understanding how the mechanics are used.
Radar is great because it achieves a lot in the design, yet is mechanically just a variant of sight. In Zero-K radar differs from sight in one way: it only reveals the approximate position of units, nothing else. The type of unit is not even revealed, although this information is remembered for previously scouted "radar dots" (to avoid fighting the UI). In terms of how the mechanics are used, the two systems could not be more different: everything has a sight range, while only a few specialist units and structures have radar. Radar can also "see" a lot further, with most radar ranges being around five times that of the average sight range. The main purpose of radar is to allow for direct interaction outside combat. By direct interaction I mean interaction with a tight feedback loop, where you and an opponent can see and respond to each other in real time. Sight alone limits players to relatively short-range interactions, which are likely to turn into fights. Various forms of dedicated scouting can allow for more out-of-combat interaction, but that risks making information too cheap. Radar admits a middle ground, one where you can respond to large scale army movements, without being overwhelmed by information or cheapening the fog of war. Of course, if you know where the enemy is, then you should be able to shoot at them (again, to avoid fighting the UI), but to expand upon the implications of then we need to take a detour into sight.
The details of sight boil down to the following question: how far should units be able to see? Our answer is, for the most part, "Just a bit further than they can shoot". This is a deliberate reversal of the situation in many other games inspired by Total Annihilation, but the idea was that it is more satisfying to fight visible units than radar dots. A more thorough justification is that vision on the enemy is tactically powerful, and that scout units mostly gate such vision behind fiddliness rather than any significant tactical or strategic decision making. This stems from the fact that scouts are cheap, can see further than the average combat unit can fire, and are fast enough for death to be a Fighting The UI problem. Mixing scouts into an army is often just optimal, since it lets everything see their targets, but giving this job to scouts mostly amounts to giving them an extra way to be stupid. So to skip this whole rigmarole, we just let units see as far as they can shoot. A notable exception to the above is artillery. Scouting targets for artillery is satisfying, as the scout has to be sent somewhere dangerous. To support this dynamic, artillery cannot see as far as it can shoot. In fact, we have a general rule that units can see 10% further than they can shoot, to a maximum of 660 range, which is is around the range of a Heavy Laser Turret. However, there are many exceptions to this rule. Some are due to technical necessity, such as the granularity of the vision grid requiring that particularly short-ranged units see a bit further. Other exceptions are deliberate design choices, such as the uniquely long sight ranges of Radar Towers, Owl, and Toad. Others, well, unarmed structures have a sight range of 273 for reasons lost to time, and the sight range of unarmed constructors appears to be essentially random.
By this point artillery seems to have two conflicting constraints: that we want to encourage spotting, and that units should be able to fire at radar dots. The solution, revealed paragraphs ago, is to make radar only reveal the approximate position of units. This is implemented via "radar wobble" - a drifting random offset of the radar dot relative to the unit's true position. Wobble discourages pot shots at dots, since they are likely to miss, so spotters have to venture out to gain vision. Radar wobble brings its own problems though, which we try to mitigate with various UI features. The main one is that radar wobble is removed for scouted structures, since structures cannot move. There is also a state toggle to tell particularly precise artillery to avoid firing at wobbly dots, although it is not enabled by default, for reasons that would require a whole extra article. What about saturation artillery? A few artillery units are far too inaccurate to care about radar wobble. In this case, shooting at radar dots is a feature. An astute reader may recall a principle that comes up in the design of cloaking, namely that it is frustrating to spend all your time telling unit to shoot at unseen enemies that you know to be present. The same issue arises with area-denial artillery, and is mostly solved by shooting at radar dots, because doing so simulates players making guesses about likely targets just outside their vision. Situations without radar, or with jammed radar, can counter this ability, but this is acceptable because the goal is to make units handle themselves in the majority of cases, just enough to alleviate the repetitiveness of always handling saturation artillery targeting manually.
By this point, it is clear that radar is central to Zero-K, and we encourage this further by making radar very cheap. Not only do commanders have free onboard radar, but the basic Radar Tower almost free. This is a great example of balancing relative to how common a unit should be, rather than by absolute usefulness. Radar Towers also perform double duty as artillery spotters, with an unusually large sight range, which incentivises players to place flimsy structures in outrageous locations, which makes for great target practice. Advanced Radar Towers have even more sight, and 250% the radar range to boot, but cost a considerable amount of metal. This makes Advanced Radar much less common, but their utility lies in viewing the enemy base, which we are less interested in encouraging. Advanced Radar also used to reduce radar wobble, however this reduces the importance of spotting for artillery, so the ability was removed. The most incongruent part of radar is the fact that radar dots have team colour. This leaks information to the enemy, yet team games rest on the idea that ownership within a team has no mechanical importance. This means that, if you know that the orange opponent has heavy tanks, then a slow orange dot is more likely to be a tank. Supreme Commander solves this with grey unidentified radar dots, and there was talk of adding such a thing to Zero-K, but I have been coming around to the idea that perhaps team colours on radar dots improves the game. At least in casual team games.
Team coloured radar dots efficiently tell your team how many opponents are present on each front, and it adds to the community feel to see who you are up against. It helps distinguish the aircraft of enemy air players, although in this case the vertical position of the dot is often sufficient. The principled stance against coloured radar dots would also advocate for removing enemy team colour entirely, turning the opposing team into an anonymous blob, which certainly feels bad for a somewhat social game. In any case, I would like to experiment with truly unidentified radar dots, but I fear the effect might be too far-reaching to measure in a short-term test. In any case, such tests will have to be postponed until the engine supports such a feature. Index of Cold Takes

• Traditional real time strategy with physically simulated units and projectiles.
  
• 100+ varied units with abilities including terrain manipulation, cloaking and jumpjets.
  
• 70+ mission galaxy-spanning campaign to be enjoyed solo or co-op with friends.
  
• Challenging, (non-cheating) skirmish AI and survival mode.
  
• Multiplayer 1v1 - 16v16, FFA, coop. ladders, replays, spectators and tournaments.
  
• PlanetWars - A multiplayer online campaign planned to start in May.
  
• Really free, no paid advantages, no unfair multiplayer.

Fully Utilized Physics

• Use small nimble units to dodge slow moving projectiles.
  
• Hide behind hills that block weapon fire, line of sight and radar.
  
• Toss units across the map with gravity guns.
  
• Transport a battleship to a hilltop - for greater views and gun range.

Manipulate the Terrain

• Wreck the battlefield with craters that bog down enemy tanks.
  
• Dig canals to bring your navy inland for a submarine-in-a-desert strike.
  
• Build ramps, bridges, entire fortress if you wish.
  
• Burn your portrait into continental crust using the planetary energy chisel.

Singleplayer Campaign and Challenging AI

• Explore the galaxy and discover technologies in our singleplayer campaign.
  
• Face a challenging AI that is neither brain-dead nor a clairvoyant cheater.
  
• Have some coop fun with friends, surviving waves of chicken-monsters.
  
• Cloaking? Resurrection? Tough choices customizing your commander.

Casual and Competitive Multiplayer

• Enjoying epic scale combat? Join our 16v16 team battles!
  
• Looking for a common goal? Fight AIs or waves of chicken-monsters.
  
• Prefer dancing on a razor's edge? Play 1v1 in ladder and tournaments.
  
• Comebacks, betrayals, emotions always running high in FFA.
  
• Want to fight for a bigger cause? Join PlanetWars, a competitive online campaign with web-game strategic elements, diplomacy and backstabbing (currently on hiatus pending an overhaul).

Power to the People

• Do what you want. No limits to camera, queue or level of control.
  
• Paint a shape, any shape, and units will move to assume your formation.
  
• Construction priorities let your builders work more efficiently.
  
• Don't want to be tied down managing every unit movement? Order units to smartly kite, strafe or zig zag bullets.

Plenty of Stuff to Explore (and Explode)

• Learn to use all of our 100+ units and play on hundreds of maps.
  
• Invent the next mad team-tactics to shock enemies and make allies laugh.
  
• Combine cloaking, teleports, shields, jumpjets, EMP, napalm, gravity guns, black hole launchers, mind control and self-replication.
  
• Tiny flea swarm that clings to walls?
  
• Jumping "cans" with steam-spike?
  
• Buoys that hide under water to ambush ships?
  
• Mechs that spew fire and enjoy being tossed from air transports?
  
• Carrier with cute helicopters?
  
• Jumping Jugglenaut with dual wielding gravity guns?
  
• Meet them in Zero-K!

• OS: Ubuntu 13.04 or equivalent
• Processor: 2.0 GHz dual core CPU with SSE (Intel Core 2 Duo or equivalent)Memory: 4 GB RAM
• Memory: 4 GB RAM
• Graphics: 512 MB graphics card with OpenGL 3 support (GeForce 8800 or equivalent)
• Storage: 6 GB available spaceAdditional Notes: 64bit only. Big Picture mode is not supported

• OS: Ubuntu 17.10 or equivalent
• Processor: 3.0 GHz quad core CPU (Intel Core i5 or equivalent)Memory: 8 GB RAM
• Memory: 8 GB RAM
• Graphics: 2048 MB graphics card with OpenGL 3 support (high GT 500 series or equivalent)Network: Broadband Internet connection
• Storage: 8 GB available spaceAdditional Notes: 64bit only. Big Picture mode is not supported