Integrating a Movement Puzzle

With this type of puzzles, the player's goal is to understand how to use the décor to travel from one point to another or to overcome an obstacle. Some readers will be surprised to find this type of gameplay in an article focusing on puzzles. However, the puzzles in Riven or Tomb Raider have a lot in common. First off, there are puzzles that block the players way and must be solved in order to advance. Secondly, the player must inspect the environment for clues. Finally, he or she must use logic to understand how to arrive at his goal.

Two categories of movement puzzles can be distinguished. In acrobatic puzzles, typical of the gameplay in Tomb Raider, the player's goal is simply to reach an exit point such as a window or an elevation. But this goal is out of reach being too far away or too high. The player must then explore the surroundings for any elements -- ledge, suspended object, etc. -- that may enable him to "put together" a way through. Tomb Raider was the game that brought this family of puzzles into the mainstream. These tasks often require dexterity on the part of the player, but that aspect is beyond the scope of this article.

	Tomb Raider

In environment puzzles, which are generally more intellectual than acrobatic puzzles, players are required to use elements found in the décor itself to unlock or reach a passage. The Half-Life series has excellent examples. In Half-Life: Opposing Forces, the player discovers a booby-trapped door connected to a detonator through an electrical cable. But the cable is severed. The solution is to push a metal can over the cable to restore the connection and blow the door open. These puzzles are, by definition, perfectly integrated into the game but this also makes them less "detectable" by the player. They can therefore be a source of dead ends, even if the puzzle itself is straightforward. The challenge for the designer is to devise puzzles that fit well into the décor while clearly standing out to the player.

As there are two categories of movement puzzles there are two sets of rules that apply to each respectively. The following are the rules for integrating acrobatic puzzles:

• Level modeling: highlight important elements in the décor. Careful observation of the décor is key to cracking these puzzles. Levels should be designed to highlight important elements in the décor, such as ledges, by using textures that stand out slightly against the general background, or by employing other visual gimmicks.
• The player must have access to an observation camera to study the décor from a different angle. The Tomb Raider camera is a trendsetter but other types of player-controlled cameras can be imagined.
• The goal to be reached (the exit) should be obvious to the player. The designer can use a carefully chosen camera angle, a cut scene or an appropriate setting to show the player his goal.
• Use visual clues. A clue such as a flock of birds taking off can be used to discretely draw the player's attention to an important element of the décor -- e.g. a platform he must reach to continue his adventure.
• Always introduce special moves. If solving a puzzle requires a special move the player hasn't mastered yet, make sure the move is introduced first.

Next, the rules for integrating environment puzzles:

• Position puzzles in dead-end situations. This way, you make sure the player discovers they are there and attempts to solve them. In Half-Life: Blue Shift, the player's advancement through the sewers is obstructed by a grinder. Loose crates drift in with the current and are inevitably shredded by the machine. The player recalls seeing a crate of explosives on the dock, and pushes it into the water. The crate then drifts along into the grinder, blows it open and clears a passage.
• Prefer simple mechanisms based on down-to-earth logic. In a realistic game universe, the player expects familiar objects to behave in a familiar way. In Half-Life, a rocket engine sitting on a testbed needs to be started to destroy a monster. The player is able to solve this rather complex puzzle (requiring several manipulations in different, remote locations) because he knows such an engine will definitely destroy anything with its blast.
• Group components of each puzzle so they are close to one another. If the components are too scattered, the player will need to make the connection first.
• Illustrate the effect of an object essential to solving the puzzle. If solving the puzzle requires an uncommon use of an object or machine, let the player know that it can be done.
  In Jedi Knight 2, the player has to destroy a huge hangar door to move on, but is still unaware of this. A huge anti-aircraft cannon is located near the door. As soon as the player settles in, enemies start to come out. The player fires the weapon for defense, but since his enemies come between the cannon and the door, the door inevitably takes cannon fire, and the player can see it beginning to break down. He has discovered where he needs to go and how to get there.