Level Design 101: Physics vs Scripted

  Welcome to another edition of Level Design 101. This time I am going to tell you a story from my previous experience helping out a friend with a project they were working on.

Note: A few details were changed in order to protect the identities of the people involved.

---

   A few years back a friend called me over to help them with this level they had been working on. The level was pretty straightforward, you run and gun yourself through a few corridors of a mansion. Eventually you come to the end of the level and you can see the ext. You're at the top of the stairs and at the center of the room is a lone NPC. It is all pretty standard but this NPC is completely unaffected by any of your shots.

   This is how it was set up. The player has the high ground and they can see the enemy on the ground below them. Above the enemy is a large chandelier. According to what my friend was going for, they wanted the player to come in and shoot the chandelier so that it would fall down and kill the enemy so the player can exit the level.

   The room was relatively empty. Just the staircase for the player to walk down from, the chandelier and the locked exit door for the player to escape from once the enemy is taken care of.

---

---

The enemy is completely unaffected by any attacks.

   The enemy will stand in the center of the room and fire at the player. If the player tries to shoot the enemy they will quickly find out that the enemy is immune to any damage. The player however is still susceptible to all damage.

   My friend wanted the player to figure out that the chandelier was the key to defeating this enemy. When the player enters the room they have a clear shot at the chains that held up the chandelier. This however is not in any way clearly stated or alluded to.

   Once the chains are shoot by the player the chandelier will fall from the ceiling and crush the enemy. This is the only way for the player to move forward to the end of the level.

   When my friend showed me this chandelier sequence, it went off without a hitch. He ran straight into the room and fired right away at the chains. The chandelier fell, the enemy was defeated and the level was completed.

   It was now my turn to give the level a try. I played through the first few rooms with no issues. I finally got to the last room and I fired straight at the chandelier....and it just swung around the ceiling. I fired at it over and over again and it just kept swinging in place. It finally just shot off the ceiling and flew into a corner of the room.

   So here is the issue. The chandelier is set to work as a "Physics Asset". The way the chandelier moves and falls is completely left to chance. I tried the sequence again and again. More often than not the chandelier would either just swing in place and if it did break free from the chain it would be thrown to some other side of the room. This meant that the enemy in the center of the room would become unbeatable and therefore the level would impossible to complete.

    Time to run the numbers. If I shot at the chandelier ten times, and it fell on target twice that would mean there would be an 80% chance of it going wrong.

  So think of it like this, if you were to knock an apple off of a tree using a rock, would you be able to make it land exactly where you wanted every time? There are so many things you would have to factor in when you through that rock, not to mention that once you hit that apple you would have no control over how fast or where it would fall. You can not predict the course it would take.

Making the chandelier rely on physics will make it's path unpredictable.

   What I suggested to my friend was for them to instead change the chandelier into a scripted event. This would mean giving the chandelier a few simple parameters that would ensure it behaved how we wanted it to. I suggested we give the chandelier a code that said "When I take damage play the falling animation". When the falling animation took affect it would follow a predetermined path that would land on the enemy crushing him every time.

   My friend was very adamant about having the chain be physics based because "It was cool". So they turned to me and said "Nope". They decided that having that random element was a lot more interesting than a scripted event. I know a lot of people hate scripted events (I do too) but in this scenario it made the most sense.

   When you have a condition such as "Enemy can only be defeated by the falling chandelier" and "Chandelier will work properly some of the time". You really see a fundamental problem forming, and you don't even have to be a game designer to see that.

---

   You never want to purposely design a "No Win Scenario". The worst part about this chandelier fiasco is that it always has the chance of going wrong. These kinds of scenarios are cheap and frustrating. No one ever wants to play a game where you fail due to things that are out of your control. As designers we should try and take as much control over the game as we can so that we may create enjoyable obstacles for players to engage in.

"Nope." - Unknown Game Designer

   I heard from a few other people that my friend went ahead and showed off their level. As I predicted the chandelier sequence broke during the run through. In fact, they had to start over three times before they gave up and ended the walk through.

---

   Physics in levels can add a great level of unpredictability, but when it interferes with design it is best to stick to something that will almost certainly work, especially if it has something to do with a puzzle. The short and long of it is, know when you should have something scripted and when something should be random.​
​

- Danny Q
@Dannylv100
​