Spelunky: A Game Design Gold Mine

Spelunky is an indie platforming game by Derek Yu. I stumbled across it, downloaded it, and was quickly absorbed into the game. The best part about this game isn't that it's free. It's that the design is solid according to the principles of Classical game design. Uncovering the intricacies of Spelunky requires a close examination of the game. Fortunately, we are well equipped with the language and the theory necessary. Let's drop a rope into this investigation and start pointing out the design gems.

Structurally, Spelunky is very similar to Super Mario Brothers. Both are 2D, contain platforming elements, enemies that can be killed by jumping on them, and power ups. And like Super Mario Brothers, the player, enemy, and level elements are designed to create a triangle of contrary motion. To understand how excellent the design is of Spelunky, we must understand how the core of the game works.  First up...

PLAYER MECHANICS

• Primary mechanics: MOVE, JUMP, BOMB, ROPE
• Secondary mechanics: WHIP, USE/ACTION, CLIMB, DUCK, RUN, FLARE, LOOK
• Tertiary mechanics: PICK UP, DROP, THROW

In general the player mechanics are all very intuitive, direct, and independent. This is almost irrelevant considering that Yu gives players the ability to customize their controls or use gamepads. I synched up my Wiimote to my PC and found these controls to work quite nicely.

The most important and impressive part of Spelunky's mechanics design is how dynamic the BOMB and ROPE are. The BOMB simply explodes after a short period of time. Just about anything that gets caught up in the explosion blows up including the player, enemies, and the level. Blow up the sides of ponds to drain the water/lava. THROW a bomb at a shop keeper to set him off in a gun toting rage. THROW a bomb to hit targets like you're throwing a rock. It won't explode until the timer runs out. You can even use the light from the explosion to temporarily illuminate dark areas.

In fact, the entire game features an extremely high level of polish and attention to detail. A fire frog enemy will lose its flame if it happens to jump into water. Leaves from plant enemies flutter down and float on top of the surface of water. Upset a shop keeper and wanted signs will be posted of your face in every shop for the rest of the game. The angry shop keepers will even leave their shops and patrol the level exits hoping to catch you. BOMB shiny areas in the walls or floors and the gold will be freed for the collecting. The list goes on and on.

Another interesting design feature of the BOMBS and ROPE mechanics are that they're limited. Players start the game with 4 of each and, unless they find/buy more, that's all they get. Unlike in games like Super Metroid, players can't simply kill/farm enemies to replenish their supplies or find recharge stations. Supplies are much harder to come by. Working with a limited supply of these powerful and versatile tools (explained below) makes each one more valuable to the player.

ENEMY ELEMENTS

There are a lot of different enemies in Spelunky. Collectively, the enemies vary in size, health, strength, speed, movement pattern, rarity, and special abilities. One of my favorite design features of the enemies in Spelunky is some of the enemies can hurt/affect each other. The man-eating plants can eat cavemen. The fire frogs create explosions like normal bombs. The arrow traps can be triggered by and kill enemies. The spikes can impale shop keepers. The aliens can kill yeti. The list goes on. It's such details that help make the core design of Spelunky so dynamic.

LEVEL ELEMENTS

The world of Spelunky is quantified to the block unit like in Super Mario Brothers. The player avatar is the size of a block. Enemies are designed to take up space by the block. Boxes and chests are a block large. Even the WHIP, BOMB, JUMP, and ROPE mechanic are measured in blocks. Because of this design feature, everything in Spelunky fits together like puzzle pieces.

Spelunky is also features a type of suspension that is completely intuitive, yet has been missing from many games. When exiting one level with an item in your hand you get to take it into the next level. You can even grab a rock on the first level, carry it throughout the whole game, and throw it in the face of the last boss. It's your rock. The game doesn't get in your way of doing whatever you want with it. It's this simple level of suspension that is very effective at connecting the gameplay from one level to the next and across the whole game. Like in Super Mario Bros (more specially SMB3), you can hold onto some of the best powerups forever as long as you don't die/get hurt.

The gold,gems, pots, crates, damsels, and other level elements, like coins in SMB, give players incentives to go out of their way. In Mario's case, coins are arranged to encourage more difficult, interesting, and superfluous JUMPing. With Spelunky, the elements encourage platforming through exploration and terrain transformation.

LEVEL DESIGN

Level design is where the core design of a game is put to the test. Without levels, players wouldn't have a place to stand on, enemies to fight, or an environment to give context and relevance to the mechanics. The levels in Spelunky have a variety of features that accentuate the well designed core (player, enemy, and level elements) as well as keep things fresh for the player.

• Solid vertical gravity design. Spelunky features all the same dynamics of gravity as Super Mario Brothers. Each jump creates a commitment on the player's part. What goes up must come down. If players aren't careful about how they jump before they leave the ground, they might end up suffering for it. In Spelunky, almost everything is affected by gravity; gold, gals, shop keepers, enemies, rocks, arrows, etc. 
• Going beyond Mario, Spelunky uses the gravity as a key dynamic in the exploration. In general, it's easy to jump down from high places. If you're not careful, and the fall distance is too great, you'll end up taking damage and collapsing in a temporary stun state. By holding down, players can use the LOOK mechanic to see far below their position. If the drop is too great to jump, players can climb down on a rope. Otherwise, the only way to keep from getting hurt is to land on top of an enemy, a maneuver that can be very risky. So, though it's easy to go down, there is a dynamic element of danger involved.
• Going up creates a different dynamic. While bombs are great for blowing up holes and dropping down through them, ropes are the most practical way of platforming upwards. Unlike falling down where the player can air control left or right, climbing a rope puts players on a strict, straight path. Though this may seem limiting compared to descending, the rope is very long can stick anywhere (even in mid air). Players can also jump off from the rope. The contrast in the paths of motion possible for ascending versus descending are especially important in that they naturally create areas of folded level design. 

• Pure organic level design. In Spelunky, the objective of each level (except the last boss level) is to get from the start of the level to the end. The possible paths the player can take to accomplish this goal are at first very limited. However, by using bombs and ropes the level can be dynamically transformed. If there's a wall/floor in your way, consider blowing a hole in it. If there's an area out of reach above you or too far below you, consider using a rope to climb up/down. Each time the player uses either of these transformative mechanics, the change is permanent. In this way, new paths can open up, intersect with old paths, or even shut off the viability of old paths. Though the goal is the same, how you get there is very flexible, and dynamic.
• Along the way from point A to B, the player is likely to decide to go after optional elements thus creating their own goals. Chests, gold, damsels, and shop keepers are all examples of elements that the player will likely go out of his/her way for. Going after these new goals naturally create small areas of folded level design. For example, going down into a small pit to get a chest and then climbing back out are two very different platforming maneuvers. This is due to the ascending-descending gravity design. With every element the player seeks adjusting the difficulty of their play experience, the potential for the paths to overlap/intersect increase due to the level transforming mechanics.
• From the start of a level, every level and enemy element are set in place. Enemies don't spawn from some unknown area off screen. For the most part, everything within a level is persistent. Due to the high level of detail put into the interactions of the various game elements, the player is free to cause chain reactions, make traps, and create strategies powered by his/her own curiosity. The game world is alive and everything works for or against everything else.
• Because the player can only carry one item at at time, juggling more than one item creates natural folds in the level design that play off of the core dynamics. For example, in dark levels, the player can use flares to illuminate the surrounding areas. When holding the flare, the player can't hold anything including a highly valued shotgun, damsel, bomb, or rope. To navigate safely through the dark while keeping up with any number of these extra items, the player must juggle putting the flare down and using the items. One time, after setting up my flares in strategic places and escorting the damsel to safely, I went back through large parts of a level just to retrieve my shotgun. It's amazing that so much dynamic gameplay comes from only being able to do one thing at a time.

• Randomly generated levels. Most of the levels in Spelunky are randomly generated. This feature forces the player to learn and apply the game rules instead of memorizing how to get through each level. Players have to think on their toes to survive. The random level generation also gives the player a better chance to experience how rich and deep the emergence/counterpoint is in Spelunky. The more you play, the more unique and interesting combinations you'll run into. And with a game that's as dynamic and detailed as Spelunky, you'll be experiencing new things for a very long time. 

• The biggest problem I have with the randomly generated levels is that the combinations will either randomly work or randomly not work. Sometimes you are forced to play in an area that you need a rope or a bomb to progress. If you don't have either of these items or an platforming powerup (see below), you're out of luck. Unlike in Nintendo games, in Spelunky there are no infinitely repawning pots/enemies to resupply the player. One time, I entered a temple level only to find a Giant Mummy right behind me already spewing killer flies (see above for dramatic reenactment). I had no chance to react. Like in the game of Solitaire, sometimes you just can't win. Ultimately, there's a tradeoff between a level you design and a level that's randomly generated. The former can be carefully crafted and highly tuned, yet remain largely unchanged with multiple playthroughs. The latter is new every time, but can be very unfocused, unforgiving, and unfunctional.

• Permadeath. In Spelunky, there are no free healing stations. Your heath doesn't regenerate if you rest for a bit. And your life doesn't come back at the start of each level. What little life (4 hits) that you start with is absolutely precious. In a world where almost everything can hurt you from your own thrown rocks, falling from too high, to your own bombs, players quickly learn that life in Spelunky is fragile. Not only will you die when playing this game, but you'll die so much, so quickly, and so easily, that you'll laugh at how easy even the most "hardcore" games are these days. When you die in Spelunky, that's it. Game over. Better luck next time.
• A pro for such an extreme penalty system is that any accomplishment, no matter how small, is a significant accomplishment. Like in Perfect Dark, my favorite FPS, beating a level means you accomplished all the objectives without dying once. Because there's no respawning, save stations, save states, or check points the only thing that can get you to the end is your own consistent skill. Like playing a piece of music from beginning to end, there's a distinct level of appreciation that you gain from doing it all in one run.
• The cons for this extreme permadeath design is that the game is more deadly than fun and there's a significant amount of trial and error in the game. To investigate a new enemy/level element, you have to interact with it (assuming you don't check a faq/wiki page). This can be very dangerous. If you die while trying to figure out just how dangerous the a Giant Mummy is, for example, you might be set back to the beginning of the game without having learned enough to keep you alive the next time. Simply getting back to another Giant Mummy is a challenge in and of itself. After a while, the player wishing to succeed is discouraged from experimenting and "playing" around because one wrong step/move can cost him/her everything. Also, whenever the game glitches and kills the player, the amount of work that is unfairly taken from the player is extremely disheartening. I got to the final boss of the game only to have the physics glitch out and kill me. I was squished while standing on top of the head of the Giant Idol. I'll probably never beat the game now.

POWERUP DESIGN

The powerups in Spelunky are almost all designed to augment the players offensive, defensive, and movement (platforming) capabilities. Click on the link above for specifics on each powerup item.

• Decay: bomb, rope, parachute, bow, and the mattock. All of these powerups decay with use.
• Offensive: bomb, machete, bow, pitcher's mit, pistol, and shotgun. 
• Movement: spike shoes, spring shoes, teleporter, jetpack, cape, climbing gloves.

All of the powerups work in unique ways. Many of them can also stack on top of each other to create a super powered spelunker. Once you obtain a powerup, as long as you can wear it or carry it, you're free to take it with you to the end of the game. This kind of suspension is very similar to Super Mario Brothers with the biggest difference being that in Super Mario Brothers, one hit from any kind of enemy will take away your powerup. I guess there's some things that are harder in Super Mario Brothers than in Spelunky after all.

In the end, Derek Yu very much succeeded in creating a fast paced, roguelike platforming game. This game is interesting and stands a very good chance of ending up on my GOTY list by the end of the year. After playing and dying more than 300 times, I have many stories to share. And with a level editor included in the package, I am free to create platforming and puzzle challenges to my heart's content. As evident with Spelunky, the tenets and principles of Classical game design are what fill a game with a certain depth and richness. It is these principles that are of a very high value these days. For those of you who haven't tried Spelunky yet, I wish you happy hunting. You'll find gold no matter if you make it out alive or not.