Balanced Melee Mapmaking
This guide is not a tutorial on how to use the Editor to create maps, there's plenty of those already. Rather, it focuses on the concepts map-makers need to be aware of to create maps that don't suck. The emphasis here is on two and four player melee maps designed for competitive play.
Creating Balanced Maps
You don't have to have a map balance to every single strength or weakness of every race. However, it's important to understand the really big weaknesses and make sure if you include one, that some compensation is put in to make the map playble for that race. Keep in mind that you can make a map that balanced in two ways: it can play to every race's strengths or balance by making every race weaker. The former is better because people like playing a good game and being able to really use their race, rather than playing a weaker one even if their opponent is too.
Protoss players more than anything need room to flank, or PvT becomes problematic. I think map-makers need to look and test where the action on a map really occurs and see if there is enough room to micro an army with flanks there. A big center area is great but if the flow of the map actually has most of the fighting in narrow valleys or ledges then it's no use.
If protoss is too close to zerg, it is a disadvantage to zerg. if zerg is too far from protoss, it is an advantage for zerg. (early game)
Refering to mineral-only naturals: Terran cannot make as many Tanks or Dropships, even worse, it is hard to make the Factories they need to establish a more solid macro game after expanding because of the gas shortage.
Zerg are the poorest race early game in defending two places at once. Zergs also need access to a second gas node during their transition from the opening to the mid-game. As Nostalgia shows, the gas node doesn't have to be a freebie at the natural per-se. A zerg's advantage is having a natural that protects the choke point leading to the main.
It's reasonable to make maps that have mineral-only naturals if they choke, or gas-naturals that don't necassarily have to choke. But doing both (having mineral-only that doesn't choke) is putting the zerg at quite a disadvantage. If the natural doesn't form a choke, I think at least the land distance between the true choke point and the natural should be somewhat minimal. A cliff overlooking a semi-baby'd natural with a long land route is fine for terran, but very problematic for zerg.
If you don't gas the natural, is it reasonable for the zerg to take a 2nd expo with gas on your map? If the closest non-island gas node is really far away that needs to be considered as a disadvantage.
Keep in mind the paths an overlord scout will make and where good places will be for the overlord to stop and scout things (such as units moving out, the opponent's gas geyser, and expos). try to keep each base's opportunity for an overlord to ferry (drop without speed) about the same.
Try to see how a sunken can be placed by a recently finished hatchery to cover the ramp and the front of the hatchery. this will determine an advantage/disadvantage for zerg.
Referring to mineral-only naturals: Zerg gets a huge advantage because Protoss cannot make Archons or High Templars in large numbers. I will say I cannot speak so much for PvZ because I don't play it, but this is a problem. As I already mentioned Zerg can still get a decent amount of Lurkers to tip things in their favor. Again though, to add more, Higher level Protosses seem to be better at expo control. Overall though I find a min nat imbalancing in this matchup.
Terran are quite flexible and can play out of one base until the mid-game if needed. They do need some way to protect themselves early vs. Protoss though via a choke point at their main, be it a ramp, opening in a wall, bridge or whatever. A 2-structure wallin (ie @9 on LT) is a nice advantage that can compensate for some other Terran disadvantage on a map.
Terrans also do well with island gas-expos that have land somewhere close to them where a CC float is timely. Obviously that can be taken to an extreme too like Gorky where the natural grants a significant advantage to Terrans because it's baby'd too.
Ledges, obstacles on the terrain, narrow areas, shorter land distances between bases and smaller base propers are all variables that can be adjusted up and down to balance Terrans against the other races.
Lastly I think Terrans benefit a little from having plenty of random build-able terrain for Turret lines. I consider this a small factor though and a good one to tinker with if your map needs some small balance adjustments.
Things to Avoid and Watch For
Test your map to check that all main gas nodes can be 3-peon'd. Count the mineral patches at each expo to make sure they're the same and roughly equal distance to the start locs.
- Mimic (recent) promap mineral arrangements, since they're (presumably) ensured to be equal, or
- Test your mineral formations using computers to ensure that they all mine at roughly the same rate (e.g. have the comps mine 4000 minerals, and at the end you should get resource scores like 1024, 1008, 992, 1008).
Make sure there's actually place to build a HQ building at expos, which sometimes people neglect.
Cliffable main minerals are possible but are going to require special balance considerations. If it's an island cliff you're really forcing your players to build countering one very powerful strat. A cliff like Bifrost though is pretty reasonable though since the ramp is right there.
Check seige range at all your expos. It's ok if they're exposed to a tank on a cliff or below somewhere, but try to make sure the equivalent expos on the other side are too. Along those same lines Stimey suggests: "When you make ridges or even islands you should also consider what a terran can fit there. if a terran can float a factory and build an addon at one ridge, try to keep it the same as the other ridges."
Don't go overboard on Critters if you use them at all. Keep in mind against a Blue opponent they're really going to wreak havoc on the mini-map.
If possible, try to avoid having a mineral-line below the HQ at mains (ie @6 LT). This really causes hell on rally points as newly made units have to weave through peons. Or with no rally point you have to select them out of a mass of moving peons which is hard too
Equalize manner-pylonablenessity of mains. This is generally more a concern horizontal mineral lines than vertical ones.
Don't get a notion in your head of some special focus the players should have. The first map I ever made had no gas at expo, no gas at any of the side expos and a 3-gas node center expo. I thought it would be cool to really have the focus on who can control that central gas expansion. I was wrong. It turned out to be stupid. Let the players actually play your map, not the other way around.
Base Sizes. Bases need to have a roughly equal ability to defend lurkers (room for bunkers) and mutas (room for turrets and bunkers).
Things to Think About
The Lost Temple expo model. You know what I mean. Gas-natural at choke, a mineral-only along the progression towards the center (not as well protected) and some islands. It's a tried and true model and a lot of good and popular maps (Gaema Gowon for instance) succeed just by incorporating the model into a new theme. If you're a beginning map-maker it might be prudent to adapt this model as well. It's not necessary to do so though. Plains to Hill is a very good map that doesn't follow it. A good rule of thumb in this: the further you deviate from the LT expo model the more carefully you have to test and consider balance for all matchups. More power to you if you can pull it off.
Symmetry. This is really popular right now as it pretty much kills any concerns about start location inbalance. The one thorn in symmetrical map makers' side of course it the lack of NW and NE facing ramps. Symmetrical maps are a good, safe way to go. Keep in mind they aren't the only way to go though. If your map isn't symmetrical but still balanced it can be a lot more fun. As much as I'm tired of this map, Lost Temple does a great job with this. There's actually very different strategies you can use depending on your start locs which makes play more interesting. I feel if you can pull off assymetry and not mess things up too much you can really make a map more fun.
Two or Four Player? 1v1 remains much more popular than 2v2 at higher levels of play. That does not mean that 2-player maps are more interesting than 4-player maps when it comes to 1v1 though. Consider the pro/cons of both when you decide. A 2-player map can have a lot of interesting things that a 4-player can't. You have more "neutral" train to fight in or do other fun things with your map. However 2-player maps can also much be more cheesable as players know the opponent's start location. I feel to avoid this cheese factor, in 2-player maps be careful placing cliffs accessible from the center and lengthen the land distance between bases. 4-player maps on the other hand require scouting and less cheese, BUT... the fact that you're going to be building 4 roughly equal bases means you have a lot less real estate to do other things with.
Mid-game Islands. I define these as being some distance away from buildable land. While Zerg and Protoss still require transport to establish islands, these types of island's really aren't a special Terran advantage as it takes them considerable time (and some risk) to float a CC long-distance. Definitely not all maps "need" these as a feature though they're a popular one for reasons Bill307 points out: I try to include 2 islands on my maps whenever possible, since I've seen so many cool game endings that result from their prescence.
Space. Impossible to wall against a top cliff edge, because workers can still move between your depot/rax and the edge of the cliff
Ash. Very limited terrain choices. Also I find it difficult to visually distinguish pass/impassable & buildable/nonbuildable terrain on this, it's very dark.
Jungle. Units (in particular lurkers) can get stuck on the ramps if they start moving around in random directions.
Desert. Don't make Desert maps. The mini-map visibility for Red, Yellow, Orange type player colors. It's also a little hard on the eyes.
Ice. Don't make Ice maps unless they are primarily grass. The hard-on-the-eyes factor of a bright white snow background. In particular protoss buildings warping in looks like crap on white background. Snow does look nice in moderation though.
Make interesting maps.. not the standard 4 bases and a middle-ground with an island or two
Just as placing temporary command centers can help you place minerals, an easy way to copy distances and keep equal distances is by placing temporary buildings or units (having the grid enabled helps). I often count how many turrets I can fit in a straight line at various places to consider adjust things.
Left/right and top/bottom terrain take up different amounts of space, so units shooting down from a ridge will vary if you simply make the space on the top and/or bottom equal. you have to trade off to make building space and the range of attack equal.
You may put a mineral on an island so that a terran cannot float a cc there (he would have to get drops like everyone else). (Referring to placing an adjusted 8-mineral patch where the CC would land , thus requiring an SCV to drop there first to pick it up).
To make a specific shape or size, again, temporary buildings make it easier. You can draw whatever shape you want with buildings and then fill in between the buildings (or around the buildings) with terrain, using undo when you make a building disappear. simply by doing this you can get all kinds of pseudosymmetry and shapes. Make sure to test, though, as top/bottom left/right and width/height are NOT equal.
Try to keep distances from one ramp to the other similar if possible, or at least with range of acceptable balance. If the distance from one base to another is way different, make sure you balance test those specific spots. the distance from a starting location to a ramp should be similar as well. An easy way to do this is to create N-1 lings (where N is the amount of spots) at each starting loc (or ramp) for one player (no random spots) and send them at the same time, one to each spot, watching to see which arrives first and how big the difference is. after doing this for all the combinations you're interested in, you can save the replay and notice how many replay seconds each route is and compare it to another map like Temple.
For perfect terrain, i suggest you get the newest SCMDraft 2.
How many mineral fields do I place? Geysers? Standard format: Main Base: One geyser, 7-10 Mineral fields (If Natural has no gas, consider a two gas main) Natural: Always one geyser unless making a CLOSE seperate gas only expo (or a double gas main), 7-8 Mineral fields Mineral Only: 6-7 Mineral Fields Gas Only: Always one gyser Other Expos (Like Islands): One Geyser, 7-8 minerals