Dynamic Difficulty in Ecco 2

Introduction

Tides of Time was quite a unique game in many different ways, one of which was its ability to automatically adjust the difficulty based on how well you were progressing through the stages, which was quite a novel concept at a time. But how exactly does this system work and what does it actually take for the skill level to change as you are playing along? This is the problem that we are going to explore in this topic.

I would like to acknowledge the work that has already been done by Johnny on reverse engineering these sections of the game when he wrote his password generator currently live on our website as this has saved me a lot of time tracking everything down. His legacy lives on and hopefully will help inspire the others along the way!

What is Dynamic Difficulty exactly?

Choose your fate

When starting a new game, the player is faced with a choice of three tunnels that correspond to difficulty level. The one directly above that has a couple of spiky shells blocking it will set game to HARD, the one next to it that goes diagonally up and to the right will choose EASY and finally going straight to the right will start a NORMAL game. It is in this mode the game will be automatically switching between Easy and Difficult depending on how well you are progressing through the levels.

Current difficulty level can be immediately judged by the size of Ecco's life and air meters: as soon as you see that they've become somewhat squashed, the game is now in Hard mode! When this is active, not only you will face additional levels, but some of the existing ones will either have extra enemies or additional puzzles to stop you!

Opinions on whether Easy or Difficult should be chosen from the start are mixed and ultimately are left to the player’s discretion. Remember: videogames are supposed to be entertaining and those seeking to frustrate themselves are going to have much more luck with Ecco 1 in that department!

Easy and Hard Difficulty

With skill levels out of the way, let’s see now how exactly does the game know how well you are doing. If you are only interested in technical details, you can skip straight to the next section, whilst here we are going to focus on what’s important to a regular player.

First of all, when a fixed difficulty level is selected, the game will actually keep track of how many times the player has died and incorporate that into the password data. This is also used when generating the Secret Password at the end. Although, given that the counter can only go up to 15, its usefulness is not entirely clear. Likewise, the information on whether Easy or Difficult mode has been selected is also stored in the password.

Normal Difficulty

Now, let us dive in and see what’s different in when in Normal mode! Here the game will no longer track player’s deaths and the same counter will now be reused for something else. At the start of the game, we are assigned a certain number of points – 12 to be exact, or 0x0C in hexadecimal. Let us call those Difficulty Points for the ease of reference. Those are then added or subtracted in the following way:

• Dying on a stage will add a FEW points to your score
• Winning a stage subtracts a FEW points
• Winning a 3D stage does NOT change your amount of points, however
• Losing a 3D stage will always ADD EXACTLY 1 point, which makes them more forgiving

The game will remain in Easy mode until our number of points has reduced to 3. As soon as this happens, subsequent wins will not decrease it any further and current skill level will switch to Hard. Losing a stage, as already mentioned, will add to the difficulty points until we have reached 31 (0x1F), after which the score will not change.

Winning stages subtracts points in a simple but clever algorithm where the game takes your current points, divides that by 4, discarding the remainder, and then subtracts that product from the points you currently have. If we plot subsequent victories starting from the initial 12, the points progression is going to be as follows:
12 -> 9 -> 7 -> 6 -> 5 -> 4 -> 3

As you can see, we need to win five levels in a row, which means you would have reached Sky Tides by the time Hard mode is activated.

Losing stages follows a more complicated algorithm with a few hand-picked conditions to allow for fair penalties as well as making sure your points do not go beyond 31. For sake of simplicity we’re going to take a case where we are currently at 3 points and lose several stages in a row:
3 -> 11 -> 15 -> 31

Quite a penalty! Without going too much further into detail to keep things simple, here is a graph that I prepared earlier to better illustrate how many flawless victories are expected from player depending on their current difficulty points to get into Hard mode again:

From this you can clearly see how the dynamic difficulty system is really geared towards being very forgiving to the player and only engaging hard mode when you are doing really well and backs down for another while as soon as you lose again. Overall this goes to show just how much more balanced in terms of difficulty Tides of Time is when compared to its predecessor.

I have tried to keep this section of the article as simple and as short as possible to explain all of the key aspects of the dynamic difficulty mechanism used in Ecco 2. Those who wish to dive even deeper are welcome to join us on the second page of this article to see just what exactly makes it work on the inside!