2 SOLO MAPS
The experience in a solo map, whether positive or negative, is derived from the story (including mission goals), monsters (their type, positioning, and number), architecture, and the interaction of the player with all of the above.
2.1 The story should dictate (or coincide with) nearly all aspects of the game.
Don't simply feed the player instructions through terminals. Write a story that brings the player into the game.
2.2 Give the players “just enough” weapons and ammo.
What is just enough? That depends on the difficulty of your map. A good rule of thumb is just enough to finish the level.
2.2.1 Avoid giving out weapons too early in the game, make players feel like they have earned them.
2.3 Monster type, placement, and number is determined by your story.
2.4 Avoid ridiculously complex, abstract puzzles that players are required to solve before moving on.
Puzzles are fine for secrets though as long as they don’t prevent the player from easily returning to the main goal of the map.
2.5 Placement of save terminals is a matter of balancing.
Having too few in a level will lead to irritation as the player dies and then has to start way back, too many lets the player save whenever they wish without fear of dying. The best placement of terminals is during pauses in the action (such as just before or after a difficult area of the map) and at the beginning and ending of a map.
2.6 The player must have a way of regenerating health in some fashion on just about every level.
However, it is easy to unbalance the map because of too much health. Using health bottles, instead of a recharge station is a partial answer to this since they can be used only once, but you might want the player to come back for more. A good guideline to follow for determining whether to place a 1x, 2x, or 3x is to think about what kind of situations the player is going to face. For most situations a 1x is fine, but sometimes the player needs more. Will the player face large numbers of monsters that deal much damage quickly? If so, consider placing a 2x. If this takes place in narrow areas consider a 3x. Also consider how far away the next recharger is. Can the player get back to this energy?
2.7 Use scenery objects to break the monotony of polygons.
Don't throw them anywhere — place items where appropriate. For example, a trail of water puddles that leads to a secret or bodies that indicate a recent battle.
2.8 Use sounds to establish a mood and add atmosphere to your map.
Add ambient noise to make the place feel alive. Every day life is filled with noises. Lack of sounds should indicate something other than laziness on the map-makers part.