In my (overly long) three-part postmortem for Horseshoe Crab Rescue! 2D (HCR2D), I focused primarily on the technical side of development and the challenges of working with GB Studio. In this article, I’ll elaborate more on some of the game design decisions that went into creating and balancing the stages for HCR2D.

Like in the original Horseshoe Crab Rescue! for the New Nintendo 3DS, the time limit for each stage is what really drives HCR2D and makes it exciting. Without the time limit, HCR2D wouldn’t be much of a game at all!

The game really gets exciting and addicting in the later stages, when the timer gets very tight and you’re often finishing the stage with less than 1 second left. However, getting the timer balance just right is tricky business – bad game or stage design, or insufficient testing, can make it difficult to balance the timer.

Limiting variability

As I previously discussed in the postmortem, the stage size of 256 x 256 is a big part of what made this tight balance possible. The larger the stage is, the more room the player would have to wander and take a sub-optimal path. This increased variability makes it difficult to balance the timer. If Joe can’t beat a stage in less than 45 seconds, but Cynthia can beat it in 35 seconds, it’s hard to find a compromise that doesn’t seem too hard to Joe or too easy to Cynthia. We could tell Joe to “git gud”, but he might just give up instead.

With smaller stages, there is less variability. There will be less difference in how fast Joe finishes vs Cynthia, and we can balance the stage in a way that makes Cynthia happy without scaring off Joe. While Joe might still struggle to finish the stages, he’ll see that he’s getting close and that will motivate him to keep trying and getting better at the game.

Maintaining player freedom

However, I didn’t want to sacrifice too much freedom for the sake of reducing variability. Although it would be easier to balance, I didn’t want HCR2D to be a game where there’s only one right way to complete each stage (except for stage 10). So I kept two goals in mind when designing the stages:

• The player should be able to find more than one valid path to completing the stage.
• There shouldn’t be a single path that’s so obvious that the player doesn’t make any effort to think about alternate paths.

To achieve this, I tried to design stages so that the player could see more than one possible direction to go from the beginning of the stage, and make sure I play-tested multiple paths for each stage to ensure there is more than one way to beat the stage. It worked out great – there’s more than one way to beat nearly every stage, and in some cases I would find that a path I expected to be slower was actually faster! In my opinion, finding your own route through a stage is one of the joys of HCR2D.

Playtesting is key

Adequate playtesting is always critical. My goal was for players to have to replay some of the later stages several times, but not so many times that they wanted to throw their Game Boy out the window. However, as the designer of a game, you will usually be much better at your game than the average playtester. There were a few stages which I could beat in one or two tries, but which playtesters really struggled with.

Another important part of playtesting this kind of stage-driven game: don’t do all of your testing in isolation. I found that I generally did better at a stage when I first balanced it after designing it (since it was fresh in my mind). In some cases, a time limit that felt right when I first designed the stage would feel unreasonably hard when I was playing through the game from start to finish. You’ll also want to ensure that there’s a gradual ramp-up of difficulty from start to finish.

Ramping up the difficulty

Most games get more difficult as you progress through the game, challenging players to improve their skills. HCR2D is no exception. The first two stages give you plenty of time to get used to the controls and look around a little. After that, you need to start actually trying to rescue all of the horseshoe crabs before time runs out. Eventually, you’ll get to a point where you probably can’t beat a stage on the first try, and by the end, some stages will likely take several tries.

Some games, particularly arcade-style games, have the difficulty constantly increasing. This is great for eating the player’s quarters, but the feeling that you “never get a break” can cause some players to feel stressed. For HCR, I decided not to try to make every stage more difficult than the previous stage. While the difficulty definitely trends upward, a particularly hard stage is often followed by an easier stage, to give the player a bit of a break.

For HCR2D, I had four ways to adjust the difficulty of a stage:

• The timer
• The number of horseshoe crabs that must be rescued
• The placement and spacing of the horseshoe crabs
• The obstacles (if any) in the stage

I tried to vary each of these parameters to keep the game feeling fresh. The early stages don’t have any obstacles, but later stages have increasingly elaborate obstacles, which makes the stages more memorable and keeps the gameplay from getting stale.

One little detail about the game that affects difficulty in an interesting way is how the rescued horseshoe crabs flee into the ocean. The horseshoe crabs are solid, so the player can’t move through them. This means that a horseshoe crab that we’ve just rescued can become a temporary obstacle. This is most noticeable in stage 20, where you really need to take their movement into account so that you don’t get trapped and run out of time.

Fine-tuning

As noted above, I had four ways to adjust the difficulty in HCR2D. To the player, however, the most obvious aspect of the difficulty is the timer. The timer is what adds tension to each stage; most players will periodically glance down at the timer and start to feel tense as they see that it’s coming down to the wire.

Because HCR2D has short stages, every second on the timer matters. If the time limit for a stage is 12 seconds and we finish with 2 or 3 seconds left, the stage can feel too easy. In some cases where a stage felt too difficult, adding even a single second could push the balance all the way over from “too hard” to “too easy”.

I considered modifying the timer system to let me set the time limit in smaller increments, such as in half-seconds. This would have made it easier to fine-tune the timer, but then I’d probably have needed to modify the HUD to show fractions of a second, which would have been too hard on performance.

So in situations where adjusting the timer by 1 second affected the difficulty too much, I then adjusted the horseshoe crab positions slightly. Moving a horseshoe crab one or two tiles can slightly affect how far the player has to walk, which in turn slightly affects how long they need to finish the stage. This helps tighten the balance without disrupting the overall design of the stage.

Time Trial mode

No matter how you balance a game, there are always going to be some players who find it too easy. Trying to balance the game for the most skilled or hardcore of players will make it too difficult for everyone else. I briefly thought about including a “hard” difficulty setting that reduced the timer slightly for each stage, but that seemed like a lazy and lackluster solution.

After mulling this over a bit, I decided to add a Time Trial mode, which is unlocked upon beating the campaign. Time Trial clocks your total playtime as you play through the campaign. This adds replay value for speed-runners and other players who want more challenge out of the game. It gives you motivation to get the best possible time on even the easiest of stages. How quickly can you get through all 20 stages?