For unskilled players, however, sentries can act as a sort of impassable barrier. They may not have the tactical positioning or teamwork skills to effectively destroy turrets, which means turrets provide "binary gameplay", something the
designers themselves were aware of. This sort of "casual player wall" is not unique to complex games: when we test our own games, we designed the puzzles, so the solutions are obvious.
Casual players may not be able to see these solutions in the same way, so no matter how obvious we consider it, we need to make sure they don't end up hitting an impassable wall.
In Practice
So how do we actually go about developing our game? Well, first off, decide what sort of game you want to make. When we started developing Cosmic Logic, we had a fairly solid idea of what we wanted: a simple puzzle game, essentially snooker/pool with a twist, which challenges the player to solve puzzles within a limited number of shots. We wanted to attract as many players as possible, so we needed to make it relatively casual, but with enough content to keep more serious gamers engaged.
Here are some basic points to consider.
How Difficult Is It to Understand the Game?
Generally speaking, serious gamers are more tolerant of tutorials than casual gamers. Serious gamers don't necessarily enjoy tutorials, but because of their "advanced gaming skill", they tend to enjoy games which are more complex. This complexity means additional rules, which must be explained.
Where Is the Challenge?
What makes your game hard? Is it devious puzzles and tests of skill, or is it lengthy boss battles and pixel-perfect jumps?
It can be hard to make the distinction between "fun hard" and "unfair hard"—all players are different, and some players may find gameplay elements frustrating that others find trivial. In fact, you can look at a game like "Super Mario Frustration", which is little more than a series of unfair challenges. It's obvious someone out there liked this, and although the market for this style of difficulty may be tiny, it does exist.
The key to testing hard vs. unfair is feedback. Watch people play your game, see which parts provide difficulty, and try to figure out where people are getting annoyed and where people are having fun. Test with everyone: children, grandparents, serious gamers, people who barely touch games. Take notes, see where they get stuck and where they get annoyed, and ask yourself if the challenge is providing a positive gameplay experience or is just obtuse.
This is exactly what we did with Cosmic Logic. I did the bulk of the initial testing myself: I've run through the game so many times I'm thoroughly sick of playing it. The advantage of this was that I could see which levels are tricky: if I'm unable to complete a level first time, then it'll likely be frustrating for a casual gamer.
Can a Challenge Be Easy and Hard at the Same Time?
This might seem like a stupid question, but easy-hard challenges have been used in gaming for some time.
The principle revolves around what the player perceives as the challenge. Winning a boss fight is hard; winning a boss fight without getting hit is harder. Some players will happily self-impose these sorts of additional rules upon themselves, but a better way to approach it is a rudimentary reward system—giving the player additional points for completing challenges with restrictions.
When you complete a level of Angry Birds, you get one to three stars to indicate how well you did. Hitman players get graded A+ to F. In Lego Marvel, collecting a certain number of studs awards the player with "True Believer" status. Getting a high score doesn't really mean anything, but it gives players an additional goal to aim for.
For Cosmic Logic, the level difficulty was designed backwards. Each level was created to have a very specific solution in mind. Once these solutions had been established (i.e. complete a level in three shots), we would then make it easier (but you have five shots to do it).
Players who could complete each level with the “true” solution would earn a gold star, and completing each level with a gold star unlocks a “bonus” ending. The gold stars and bonus ending don't really change the way the game is played, but they ensure that players have something to aim for beyond simply crashing through levels.
What Happens If I Fail a Challenge?
With any challenge comes the possibility of failure. It's important that we make the separation between failing the player and punishing the player, however. As we said earlier, challenges are only fun while a player hasn't "solved" them. If we make a player go back to the very start of the game every time they die, then it's very likely they'll get bored of seeing the first level very quickly.
In a skill-based game (such as a platformer or first-person shooter), there is some leeway in making the player repeat content, as the longer they play the game, the better they get at it (hopefully). With a puzzle game, this leeway doesn't exist, meaning puzzles are often very binary: either a player can solve it, or they can't. If they can solve it, then great—unless they die and have to solve it again. If they are unable to solve it, then the player becomes stuck.
There are several ways to avoid this problem. The first option, used by games like flow free, is simply to make all levels open to the player at the start of the game. In flow free, every level is unlocked. Players can choose which puzzles to solve at their leisure, and can entirely skip the first half of the game if they so desire. Flow free has so many levels that skipping a few doesn't really affect the game, but for a more "story-driven" game (such as Mario), allowing a player to skip right to the last level might not be an option.
Another possibility is allowing a player to skip levels. Some puzzle games allow a player to skip a certain amount of levels: a player might have three free passes at the start of the game, which means that particularly hard levels can be avoided. This can be partially replicated in other games, by giving the player branching paths, optional fights, or even warp pipes to allow them to skip content.
In Cosmic Logic, we took a third approach: making each level incredibly easy. As we mentioned above, we had an idea of how each level was to be completed, and we simply allowed the player additional shots for them to complete it. We wanted to avoid a level skip mechanic, for there is a gradual learning curve—something you used on level 11 might be necessary to complete level 25. We wanted players to grasp the fundamental concepts of how to play the game, so we simply gave them the leeway to be really bad at it.
Does the Game Get Harder as the Skill of the Player Increases?
This is a problem that simple games can face. If you're playing something like Space Invaders, then once a player has cleared a few waves, they have essentially "mastered" the game, and it will no longer provide a challenge.
Most games use a difficulty curve system, which is what we did with Cosmic Logic. As the game progresses, the player learns more ways to clear tables, and new challenges are provided to ensure they are constantly challenged. Nearly all games with a level system use this mechanic.
However, not all games use level systems. For "endless" games, having the difficulty increase as the player continues is one option: but if the player has to play through "easy" content to get to the fun part, then the game might just be boring.
This was one of the major flaws of
Starbyte, another game I worked on some time ago. In retrospect, allowing the player to select a difficulty level would have been smart, but at the time we decided that simply increasing the game's difficulty as the player progressed would be enough. In practice, it meant that the game got too hard too quickly for novice players, and was too easy for too long for advanced players.
A game doesn't necessarily have to be harder to be fun, though: allowing the player to skip through easy levels, or even offering a "turbo" button, allowing the player to play at double speed and thereby cruising through the simple challenges, are simple but effective ways of keeping your more skilled players engaged.
Bringing It Together
Not all of these techniques are applicable for all games, but they're worth thinking about. A good general rule of thumb for providing a challenge is: "Is this something the player can be realistically expected to do, or are they going to fail?"
There's nothing wrong with failure, but players don't want to feel cheated out of victory. If a player says, "Well, I should have jumped earlier, that was my fault," then you've provided a good challenge. If a player says, "There was literally no way for me to avoid that," then you're punishing the player for no reason. Most of these design techniques are applicable to all games, as no player likes unfair gameplay.
And remember: although we like to talk about a casual/hardcore divide in gaming, this divide is somewhat arbitrary. With careful planning, there's no reason a good game can't be enjoyed by everyone—and if a four-year-old child can enjoy Grand Theft Auto, what else can we achieve?