8 Principles of Good Game Design

Here, I will gather all my previous posts about what makes a good computer game. Or you can download the pdf here.

Principle 1: Meaningful Play:
“Meaningful play is what occurs when the relationships between actions and outcomes in a game are both discernable and integrated into the larger context of the game.” (Salen & Zimmerman in “Rules of Play”, 2004)

Meaningful play is one of the most basic principles of good game design. It states that inputs (your interactions with the game) and outputs (the visual and audio feedback of your interactions) must be meaningful to the player. They must make sense. For example, when walking into a gloomy forest with our character (input), music could change to accomodate the mood here (output). When choosing a warrior avatar as opposed to a thief (input), we should feel an increased amount strength in battle (output). When throwing bombs at enemies (input), an explosion should appear, killing nearby enemies (output). On a more general level, player actions should be integrated or woven into a larger event happening in the game. All these examples create a very basic logic connection between what you do as a player and what plays out on the screen, which provides incentive for the player to keep playing. Conversely, when player actions lack discernable outcomes - when the player can't perceive the immediate outcome of an action, trial-error incidents tend to occur. As players, we keep trying and failing, because our understanding of the consequences of our game actions is unclear. This should be avoided in order to achieve meaningful play.

Principle found in: Halo:
halo meaningful play
In the Halo series, your actions – to rebel against an evil alien force – clearly make sense in a larger context. The human race is at war, and you’re a vital instrument in winning it. Thus, it makes sense that you spend most of your time gunning down aliens. Doing other stuff wouldn’t make sense for a soldier such as Master Chief.

Regardless of whether your shooting with a weapon, hurling an incendiary grenade, jumping, or driving vehicles, you receive an output that makes sense. The same applies to the AI. A small enemy - having seen all his comrades die - might panic. The giant axe-wielding enemies come charging at you with devasting results. Allied characters prompt you to go into cover when in danger. All these AI reactions to your actions make sense to you - they generally feel intuitive within their context.
halo master chief

Also, the battles rarely rely on trial-error. The levels are designed in such a way that you’re mostly presented with an area, in which to eliminate all enemies to progress. The goal is very simple and clear to you. And you won’t experience enemies suddenly spawning behind you or “cheating” in other ways. When you die, it’s mostly due a tactical mistake from your part – because you’ve charged forward too aggressively. You tend to know exactly why you died, enabling you to correct the mistake afterwards. There is a certain discernibility between your player actions and their outcomes, which limits trial/error. Trial/error is also diminished by the fact that you can take relatively many shots before dying. Imagine how frustrating one-shot-kills would be in Halo. You would die without even knowing what happened. (Actually this does occur in some of the sniping missions in Halo, which is why these are my least favorite levels of the game.) But, generally Halo should be commended for its high degree of meaningful play. There is usually intent and expectation behind every player action, and the result usually has some relevance and significance. This is what meaningful play is all about.

Principle 2: Gameplay Balance
“When players have multiple options or routes to victory, each option or route should have a risk-reward relationship that prevents dominant strategies. The level design, in particular, should accommodate this feature.”

In most games, you can complete a task in several ways. You might be able to choose different playable characters, weapons, or tools before a mission. There might also be different routes to victory – for example a shortcut in a racing game. The amount of solution options obviously varies a lot from game to game. Some are very open while others offer a more linear progression. Nevertheless, it’s important that the players are put in a dilemma about which option to choose. A shortcut in a racing game has the obvious advantage – or reward – of being quicker. ‘However to compensate for this advantage, the game designer could make this route more difficult – by making it more narrow and full of tight turns, for instance. This will make the player’s choice interesting. Should he risk taking the shorter more difficult route, or opt for the safe one? The decision might depend on his current position in the race, his skill level, his mood and so forth. On the other hand, if the short cut is undeniably better in all situations, taking it would be a dominant strategy, removing these satisfying considerations.

The same thing is seen in strategy and role-playing game, in which you choose a race in the beginning. Here, it’s also important that no race always triumphs. Otherwise, why even include the others in the game. Blizzard, in particular, is known for mastering this game design principle, constantly releasing patches to level the playing field between races.

So in conclusion, forcing the player into making strategic, interesting considerations is a basic principle of game design. This goes well together with Sid Meier’s well known quote: "A [good] game is a series of interesting choices"

Principle found in: Resident Evil 5.
Resident Evil 5 has a mode called Mercenaries. Here, you must kill as many zombies as possible within a set time frame. You can obviously shoot the zombies, but you can also go into close combat. This sets up an interesting choice of risk-reward. The safest solution would be to keep your distance, and take them out one by one, After all, zombies are much more lethal in close combat. However, this solution uses up valuable ammo. What’s more, killing a zombie with a close combat move, gives you extra time, in which to kill more zombies and increase your score. This is a significant and tempting reward for an otherwise risky action. If you miss your close combat attack, you risk death.

As a player, you are constantly faced with these interesting choices – using the gun or your fisticuffs. Your decision is influenced by many factors, including the zombie’s remaining health, the number of zombies in the area, your current score, the remaining time, etc. These considerations represent a very satisfying challenge that could not materialise without gameplay balance. If one strategy had been the most dominant in all situations, you would lose this appealing aspect of games.

Principle 3: Provide positive and negative feedback
“The player should clearly and almost constantly be told whether his actions had a negative or positive effect on achieving his goal.”

One of the most frustrating game situations happens when we are unaware of whether our actions bring us closer or further away from our goal. Many boss battles suffer from this. You keep pounding bullets into the gut of the boss, but nothing seems to happen. He just keeps on accepting them, without even reacting at all. Is he just extremely tough or is the player missing some sweet spot that needs to be hit? This is frustrating not to know, and it will likely result in the player getting stuck.

Likewise, in first person shooters, it’s important that an enemy reacts realistically upon being hit. He should perhaps fall to his knee after taking a shot in the leg, or lose his head after a head-shot. Animations are vital in communicating this feedback. Apart from being more realistic, thus immersing the player more, these reactions also make the player feel more empowered. You feel as if your influence over your surroundings is that much more significant, which makes the game infinitely more rewarding to play.

Obviously, there are many other ways to show or enhance the feedback mechanism. Score increases and health meters are certainly among them. Particle effects, such as blood splattering, can also enhance feedback. Sound is important too. A scream of agony coming from an enemy indicates very clearly that you’ve done successful damage. The characteristic tune playing when Mario dies also deserves mention.

Principle found in Tetris:
tetris feedback
Tetris is an obvious example of constant feedback. At all times, you know exactly how well you’re doing just by looking at the height of the Tetris tower, which is always in focus, anyway. The height is updated constantly. As soon as you make a line disappear, the game shows you how the tower is diminished. Conversely, if you can’t get the bricks to fit, you instantly experience how the tower grows taller – ever closer to reaching game over. This visual feedback is complemented by constant score increases and music that is intensified in critical situations.

Principle also found in Call of Duty: Modern Warfare:
modern warfare call of duty feedback
The multiplayer mode in Modern Warfare is also a prime example. When you’ve killed an opposing player, you instantly see points on the screen, showing your increased experience. Making a headshot even plays a very distinct “bullet-to-skull” sound, which is immensely satisfying to hear. What’s more, the overall score is always shown at the top of the screen. Also, negative feedback is prominent when you become hit. Besides force-feedback in the controller, you see red arrows showing where the shot came from, and sounds get distorted while the screen blurs, becoming redder as your death approaches.

I realize, that this principle isn’t universally applicable to all games in all genres. Giving constant feedback doesn’t really match real-life experience. We don’t see a status display, in the top right-hand corner, when taking a walk in the park, for instance. We aren’t constantly evaluated in our daily lives. Therefore, games that strive for highly realistic gameplay could benefit from avoiding this principle – at least partially.

Principle 4: Flow in Games
“Get players to experience flow”:

The flow theory is used in psychology and developed by
Csikszentmihalyi in 1990 in his book "Flow: The Psychology of Optimal Experience". He has observed how some activities, such as painting, mountain-climbing, and other leisure sports, are often carried out simply because we want to. There is no external, material reward connected to these activities. Instead, our motivation is to get into a flow state - a basic human desire. The flow state is one of intense immersion, in which our attention and concentration completely revolve around a certain activity. There is a loss of the feeling of self-consciousness, a merging of action and awareness, and no place for thoughts unrelated to the activity. In flow, you feel as if you alone can affect your fate. The idiom ”to be in the zone” summarizes this state fairly well. Though flow isn’t specifically aimed at games, but has a broader scope, Csikszentmihalyi specifically mentions games as potentially flow-inducing.

So how should we bring players into flow? Csikszentmihalyi sets up several necessary criteria. First off, the difficulty has to match our abilities, so we are suitably challenged. This is a fine balance. A game, which is too easy, gets us more easily distracted by other things. If too hard, we get frustrated. The game has to strike the right balance and keep getting more difficult as we improve our skills. Having multiple difficulty options at the start of the game is obviously a good starting point, as players’ general game-playing abilities differ wildly. An increasing difficulty curve, where gameplay gets progressively more complex, and follows players’ skill developments is also vital. In order to achieve this balance, extensive play-testing is required.

A single, clearly defined overall goal is also important. Without it, we can’t keep an intense focus on the task at hand. This actually goes well with my first principle, stating that unwanted and distracting trial-error incidents tend to occur when our goal is unclear.

Feedback mechanisms are also vital, which is exactly what my third principle deals with. We need to constantly be told whether we are getting closer to or further away from our goal. This keeps us motivated.

We also need a sense of control in an otherwise uncertain situation. Again, this is a question of balance. If the game plays itself too much, we are unlikely to experience flow, because we lack a sense of empowerment. On the other hand, if the empowerment is so strong that we can easily control our surroundings, the challenge is compromised. Imagine dying in a game and just restarting exactly at the same spot with no loss experienced. There would be no incentive for us to concentrate on the task. We would be practically immortal – too empowered. Thus there has to be some frightening, chaotic elements – that keep us on our toes and reminds us that the risk of failure is always looming just around the corner.

Principle found in Geometry Wars:
geometry wars chaosMany puzzle games considerably adhere to this principle. Geometry Wars is certainly one of them – perhaps the most extreme together with Tetris.

In Geometry Wars, the goal is very clear: It’s all about surviving the hordes of enemies spawning in endless waves. Feedback mechanisms are plentiful too. Colorful particles spawn upon enemy destruction, and score increases and power-ups reward the player often. There’s also an increasing difficulty curve, making sure that enemies get harder and more numerous as a game session proceeds. Finally, you do indeed feel a sense of control in an otherwise chaotic environment. The game feels immensely chaotic as dozens of triangular shapes move about on the screen shooting at you, while bombs and vortexes frequently inhabit the screen. Your heart is pumping as you narrowly avoid an enemy and just manages too shoot a suicidal space ship before impact. These actions are made all the more nerve-wrecking as the consequences of failure are severe: you have to restart entirely. The sense of being constantly "in the zone” is supported by a hypnotizing trance beat.

Despite the amount of chaos, a good player can survive for a long time, indicating that the game is immensely skill-based and that it’s possible to exercise some degree of control over this this insanely chaotic play field.

 Principle also found in: Undo 9-11:

Our own game, Undo 9-11 greatly adheres to this mechanic in a very simple way. In Undo 9-11, the player must prevent the terrorist attacks of 9-11 by shooting down planes before they reach the World Trade Center. This is done with a laser gun, that shoots in a straight line making multi-kills possible. The game starts out easy, but, quickly, the increasing spawn rate of terrorist airplanes makes the game gradually more challenging. The better the player becomes, the harder the challenge.

You can try the game out for free on facebook here.

Or get it free on Android here. 

Principle 5: Easy to Learn – Difficult to Master

“All the best games are easy to learn and difficult to master. They should reward the first quarter and the hundredth”. – Nolan Bushnell

While I don’t think that all games should follow this principle (afterall, many games for the hardcore players in particular can benefit from starting off in a complex and difficult manner in order to avoid boring the generally experienced target audience), it is still a valuable general guideline – especially for casual and mobile game developers.

It is particularly important for their audience not to experience frustration but success shortly after starting the game the first time. You have to capture their interest immediately – put a smile on their face within few minutes. A tutorial can be necessary to communicate what the game is about, but keep it concise and easy-to-understand.

Also, make sure that the game is based on a single, simple gameplay mechanic that makes sense in the context of the game (see also part 1 on meaningful play). To test this, check if the gameplay can be explained with a simple verb and object. It could be “throw bombs”, “aim pistol”, “avoid enemies”, or "cut the rope" (pun intended). If this test fails, your target audience might belong to less casual players.

To ensure the longevity of the game, an increasing difficulty curve must be implemented. New challenges, tools, enemies, power-ups etc, must be gradually included to complicate the underlying gameplay mechanic. Make sure you build upon past player experiences, bridging the gap between the known and the unknown. Introduce one new feature at a time. If successful, the player might play until the very end when most gameplay elements exist together, culminating in a complex and maybe even chaotic design that demands much focus and concentration. The player will feel that his skills have come a long way since he booted up the game for the first time.

Finally, this principle can also be met by making sure that each section or level of the game can be completed in several ways that are rated differently. For example, you can give scores or stars to the player depending on his performance. In this way, both bad and good players can have their own incentives to play a specific level – and longevity is boosted when the desire to improve your score settles in.

Principle found in Tiny Wings:
tiny wings easy to learn difficult to master
Tiny Wings for the iPhone and Ipod Touch, is extremely simple. You control a small bird, trying to fly over a bunch of hills in a 2D environment. You must get as far as possible within a set amount of time. When not pressing anything, you float in the air slowly drifting down. While touching anywhere on the screen, you fall down quickly. You must use this mechanic to land on downhill slopes in order to get momentum and speed. In other words, Tiny Wings is all about timing. The mechanic is extremely easy is to learn – and complemented by a simple tutorial with a few informative pictures. When you’re doing
poorly, the speed of your bird is automatically slowed down, since you lack the momentum gained when playing well. This slow pace gives beginners a larger time frame in which to time their landings. Conversely, the more momentum and speed gained (in other the words: the better you get at the game), the more difficult the game becomes. Landing on a downhill slope is much harder when blazing through the skies with tremendous pace. This built-in gameplay mechanic thus perfectly supports this design principle.
tiny wings random
Furthermore, the game has optional power-ups, such as jump pads and food that increase your score. Taking advantage of these becomes especially important for the hard-core gamer that wishes to beat his high-score. Also, special awards are given for playing in particular ways, which encourages multiple play-throughs. These are optional tasks implicit in the game and mainly directed at experienced players looking for additional challenge.

Principle 6: Rewarding the Player

“Reward the player with more than just score increases. Include rewards that expand gameplay itself”

Positive reinforcement is well known for being a great motivator. Getting praise makes us happy, boosts our confidence, and pushes our efforts further. This is already briefly mentioned in the third principle regarding the importance of giving out positive feedback. This sixth principle is a more in-depth account on how the player should be rewarded.

Giving out scores is one of the oldest and most widely used techniques. When the game is over we get a score, summarizing our efforts with a single number, typically reaching into the thousands. This encourages several play-throughs, as we try to beat our high-score – a motivation that is increased when the high-score list is integrated in an online system with friends and other people competing. Bragging rights can be big motivation factor, making score systems – including achievements – a valuable asset to your game.

As game designers, we can motivate players even more by making some rewards useful in the game design itself. Just getting a score is not a tangible, useful reward within the game. It’s just a number. Just like in real-life getting a useful present is much nicer than a simple pad on the back.

So what should this present be like? Fortunately, there are countless answers. Unlocking new areas is one of them. Some games have special, advanced levels unlocked only when a specific, difficult requirement is met. Getting new weapons or tools – also known as loot - is an option too, and in role-playing games, you’re often rewarded with extra abilities and skills as well. Apart from empowering the player, these approaches provide an extra layer of complexity to the gameplay thus supporting an increased difficulty curve as a bonus feature. A reward can also be audio-visual or be related to the story – for example, a beautiful cut-scene explaining tidbits in the story – like in the Final Fantasy games.

In extreme cases, the rewards can also be more integrated in reality, as in World of Warcraft where you can earn real money by selling your virtual character and goods on auction sites, or Little Big Planet where you can use your level design retorically or as part of a viral marketing campaign. Of course, these actions are not a direct component of the game design of these games, but they still represent a considerable motivation factor for many people. On a side note, we see more and more games expanding into the realm of reality when it comes to rewarding the player (look up ubiquitous gaming, pervasive gaming, or see my thesis The Expansion of Computer Games Beyond Ludology for more details)

Principle found in: Super Metroid
super metroid reward
All the Metroid games have extensive reward mechanisms that go way beyond scores. You control Samus, a lonely bounty hunter, out to destroy the evil Mother Brain. In the beginning, your arsenal and abilities are extremely limited. You’re weak – both defensively and offensively. You often gain tempting glimpses of areas and items unaccessible until you get a specific weapon or tool later on. For example, getting the grappling hook - upon destroying a boss - is an immensely satisfying reward, not only empowering you, but also giving you access to so many new areas. Weapon and ammo upgrades, health increases, and abilities such as wall-jumping also make up your rewards. They are a lot more interesting than scores because they are useful, fun to use, complicates gameplay, open up new areas, and empower you in your overall objective. Scores can never achieve these effects.

As a side note: upon completing the game, you don’t get a score per se. However, depending on your completion time, you see Samus take off an increasing amount of her clothes – another interesting way of rewarding the (male) player☺

Principle 7: Let the computer do the tedious work

As opposed to board games, computer games can use the computer to automate or simulate certain actions or events. The computer can make stuff happen outside of manual player control. Characters can be programmed to move - independent of player actions. The weather system in the game might change. Buildings may suddenly collapse.

A computer game designer can use these features to his advantage. He can limit player actions to what is interesting, letting the computer handle the tedious work. As stated in the second principle, a good game is a series of interesting choices. The elimination of uninteresting ones thus represents an important game design principle.

The use of teleportation mechanics is a well-known example in this regard. Instead of forcing the player to travel long distances, which can be tedious, the ability to teleport can optimize the pace of the game considerably, leading to a more entertaining and varied experience. Making sure that the players don’t spend hours in a virtual fitness center with their avatar before a fight in a beat-em-up is also a useful example. Not having to manage inventory, navigate interfaces, or do other administrative tasks can also enhance the entertainment value.

In the driving game genre, we see more examples. What is interesting about being a race driver is the thrill and exhilaration experienced by the sense of speed. Generating this feeling is the focus for most driving games. You typically don’t’ spend hours preparing for a race, analyzing tracks, and evaluating your performance meticulously after a race - actions that would be necessary for a real driver. Even the driving experience itself is often limited to speed and brake controls, because these are the most interesting. Operating other mechanics such as shifting gears is often neglected, partially or completely.
This act of simplifying real-life behaviors is a common trait of computer games – and an important one in order to keep games interesting.

Principle found in: Mario Power Tennis

The Mario Tennis games simplify what tennis is all about in its most entertaining essence. The satisfaction gained when hammering a perfect baseline hit, doing a well-adjusted lob, a great volley, or an unbelievable save is emphasized considerably in Mario Power Tennis via its use of special attacks. These can be executed often either defensively – to save an otherwise impossible shot – or offensively – to hammer the ball with utmost precision and speed. Conversely, what is generally perceived as less interesting about tennis is ignored. All the strategic aspects are more or less gone. Even the act of hitting the ball out of bounds happens fairly infrequently, because it’s less fun than determining a duel with a winning shot.

Again, this principle should not be followed religiously if you’re making a highly realistic game. In the real world, we can’t always let the computer do the tedious work (and we certainly can’t teleport ourselves), so using this game design technique might break the immersion of participating in a real world.

Principle 8 - The Importance of a Solid Core Gameplay Mechanic

“Make sure the most fundamental player action is fun. Build your game around this core mechanic.”

Most successful games are built around a simple, fun gameplay mechanic. This is the most fundamental and frequent action you perform as the player. If this action is boring or unfulfilling, it doesn’t matter how many twists or extra features you add to the game. They can’t save your game design.

This core game mechanic must be intuitive and relatively easy to learn, because learning a mechanic is never as interesting as utilizing it as a means to completing your goal. In other words, learning time should be minimized. In order to increase the complexity and challenge level as the game progresses and player skills improve, small extra features also known as “satellite mechanics” should be introduced. These provide twists to the core gameplay mechanic, forcing the player to use it in a slightly different and more challenging way.

Game developers should minimize the learning time of these satellite mechanics too. This can be done by making sure that they are connected to the core gameplay mechanic in a logical, intuitive, and meaningful manner (see the first principle on “Meaningful Play”). The trampoline in Super Mario Bros. is a great example. Its function instantly clicks with you. You understand why it’s there and what it does – its implementation is meaningful. You might also want to minimise the amount of satellite mechanics, so the player doesn’t have to learn new ones constantly. In particular, if two mechanics have similar functions – if they are relatively redundant - delete one of them from your game. Or perhaps you can redesign one of them to have multiple functions (i.e. a lightsaber that can both deflect lasers and cut through enemies in close combat). Nonetheless, it’s important to beware of “feature-creep”! Kill your darlings! Don’t spam your game with huge amounts of satellite mechanics – that approach will just increase learning time.

Once all the satellite mechanics are introduced, make sure to switch them up in order to create a varied gameplay experience. Avoid using one for a while in order to renew player interest in it. If several satellite mechanics work together in interesting ways, exploit these relationships to bolster gameplay variation even further.

Principle found in: Angry Birds

Angry Birds is based on a single core mechanic: catapulting birds towards pigs. This action must be done hundreds of times in order to complete the game, and it’s very easy to get to grips with. Even small children understand the logic behind catapults. In order to complicate gameplay, various satellite mechanics are gradually introduced. The inclusion of several bird types – each with their own special attack - is one of them. The placement of TNT barrels that explode upon impact is another example. And the fact that some objects give bonus points when hit also serves to make the game harder to master. These satellite mechanics are instantly learned and seamlessly integrated with each other and the core gameplay mechanic.

Final remarks

UFO ZAP game designI hope this all makes sense. If it does, please like it on Facebook. As already stated, these principles are just general guidelines, not a rule book for good game design. These principles are certainly something we at Red Key Blue Key consider in our own games - not least in our latest release UFO ZAP.  

What Makes a Successful Casual Game

When looking at the most popular and best-selling games for iPhone, iPad, and Android platforms, they generally share a remarkable number of features. In this editorial, I will analyze what the most popular games have in common in order to answer the more general question: What makes a game successful on mobile platforms? Games like Angry Birds, Cut the Rope, Tiny Wings, Flappy Bird, Fruit Ninja, and Jetpack Joyride are all highly successful mobile games. They generally possess a number of shared features, which I will explain below.

A very limited number of gameplay mechanics:
On a very broad level, the developers of the above-mentioned games have understood what the general mobile game player seeks in a game - what motivates him to play. They know that mobile players tend to be casual players - rather than highly experienced ones. First and foremost, this means that the game has to be easy to learn and understand. Therefore, these games have very few different gameplay mechanics. You tend to do the same action over and over again. This core gameplay mechanic instantly clicks with you because it resonates with something you already know from the real world. Whether it is the logic behind catapults as in Angry Birds, the logic behind rope cutting as in Cut the Rope or the slicing of fruit as in Fruit Ninja, the relationship between what you do, and what plays out on the screen seems intuitive and logical.  In other words, these games heavily support the notion of "meaningful play" as explained in this former blog post. When a new feature does crop up, it is gradually introduced and complemented by a short uninterrupting tutorial, clearly showing its underlying logic.

Little input, big output:
In these games, you set something in motion with a simple input, and get a huge amount of feedback usually generated by physics. In Fruit Ninja, a simple swipe generates numerous huge, colorful fruit explosions. In Angry Birds, you catapult your bird with a similarly simple swipe, after which buildings collapse, bricks explode, and pigs fall on each other in a chaotic and rather unpredictable mess.
Angry Birds input output This relationship between simple inputs and magnificent outputs creates a great feeling of empowerment in players, who instantly see their simple actions have considerable impacts on the game world.

Physics-based gameplay:
These "considerable impacts" are usually generated by physics. Nearly all successful mobile games are physics-based. They force players to master - or predict - the laws physics in order to achieve success. This approach seems to be clever for a number of reasons. First of all, physics tend to be responsible for numerous emergent gameplay variations, thus providing variety to an otherwise simple game. What's more, the inclusion of physics makes it easier for the player to understand the outcomes of his actions, because he's familiar with the laws of physics from everyday life, thus supporting the notion of "meaningful play", as explained earlier.

A bright, cartoony, and cute visual style:
Angry Birds visual styleBoth the angry birds in Angry Birds, Omnom in Cut the Rope, or the little bird in Tiny Wings look very expressive and cute. With their big eyes and cartoony outline, they tend to appeal to people of all genders, ages and nationality. As a result, these characters become likeable, and we might even see part of us reflected in them. We immediately create a very basic emotional connection to them. This connection appears to be hugely important - especially for casual gamers. It would be significantly harder to achieve this connection without a cartoony look for a number of reasons. First of all, the small screen size of a phone forces the developer to exaggerate a given expression in order to communicate it. This exaggeration makes sense in a cartoon world. Secondly, the lack of horsepower provided by current mobile devices limits the possibility of creating compelling and credible realistic-looking characters and game worlds.

A very simple storyline:
In order to accentuate the aforementioned emotional connection, a very basic and lighthearted storyline is often set up. Oftentimes at can be summarized with a single sentence. It sets up your character's basic motivation - something irritating or dangerous that needs to be taken care of. Again these storylines tend to have a very universal appeal. Whether bird mothers experience the kidnapping of their eggs, or Omnom needs candy, the story instantly clicks with you - no matter what culture you come from. You understand why the characters do what they do, and you want to help them succeed.

The player is constantly rewarded:
After each play-through of a level, players are rewarded with stars, coins, or highscores or a combination of them, and usually they are accompanied by satisfying and exaggerated sound and graphic effects. This reward-giving act happens extremely frequently in the above-mentioned games. Their developers have understood that for mobile game players, instant gratification is particularly important, as they generally can't muster the amount patience or can't invest the amount of time that traditional hardcore gamers can. These rewards not only provide positive feedback - thus motivating the player to continue playing, they also boost replay value as players revisit levels with sub-optimal scores. Why this constant reward mechanism is generally an important game design principle is further elaborated in this blog post.

A huge amount of levels that are very short...:
It's common for these games to have many bite-sized levels - sometimes over 100. Being bite-sized makes them easy to pick up and play when the player has little play time at his disposal. Sometimes, they take less than 5 seconds to complete. What's more, this structure supports the aforementioned instant gratification that mobile players crave for.

...Or one level played over and over again with random elements:
If these games don't have huge amount of small levels, they tend to adhere to a single level structure as seen in Tiny Wings, JetPack Joyride and Flappy Bird.
Tiny wings one levelHere you play the same level over and over again. Random occurrences serve to differentiate play-throughs, and oftentimes you must complete specific assignments during a play-through. This model is similar to the handheld classic, Tetris, in that the act of surviving for as long as possible in an increasingly difficult game world is a key feature.

2D side-scrolling gameplay:
2D games are seeing a huge revitalization on mobile platforms - not only because the hardware limits complex 3d geometry, but also because 2D games tend to be inherently easier to understand for the casual player.

And the rest...:
Here, I will mention a couple of minor feature enhancements also present in most successful mobile games. The inclusion of leader boards and achievements via services such as OpenFeint and Game Center is one of them. Frequently updating the game with additional content and features is important too. A general high degree of polish, as well as a very low price point - rarely exceeding 3 $ - can also help sales.

As a developer for IOS, I think it can be valuable to look at how many of these features you have included or can include in your game. This post shouldn't be seen as a simple checklist, though. Rather, it's a general guideline for successful mobile game design. It's certainly something that we at Red Key Blue Key have considered greatly in the development of our latest game UFO ZAP.


UFO ZAP game designhttps://www.facebook.com/appcenter/694654913926300?preview=1&locale=en_UShttps://apps.facebook.com/694654913926300/?fb_source=appcenter&fb_appcenter=1