Black Golem

Nordenfelt 0.2 has a little secret:

Try to NOT beat the end boss for at least two minutes and the world ends!

This "bug" has a simple reason: the level background is finite. This is a problem for boss fights which last longer than expected. After pondering a while and some talk with kapiezi I came up with a few solutions which I want to show you here.

Stop Scrolling While Fighting The Boss

This solution is easy to implement but may destroy the illusion of flight. It depends on your ship type as well as on the boss type. It will be fine if you're controlling a helicopter, jump jet or a medieval dragon. All these avatars can hover above a position. However, authentic war planes can't (WWII and before) and therefore should not be used for scroll stopping levels.

The boss itself may be immobile, e.g. a big turret. This is a good reason to stop scrolling. Nevertheless, keep the type of your player ship in mind.

Let The Boss Commit Suicide When The Level Ends

That sounds even simpler than the former idea. A timer or spatial trigger is enough here to solve the finite level problem. The player will be happy to. She just has to wait for the boss to explode. How can we compensate that? Well, the boss may become more angry, fire more bullets or move faster over time. The rage should ramp up to impossible-to-master difficulty when the level ends. A little humble but it should work.

The Level Restarts When You Reach The End

This is similar to letting the boss destroy itself. Level length and scroll speed define the time frame within the level has to be won. Otherwise it has to be replayed. I'm not a friend of this. If the finite level length is the only reason for a time limit it should not be used. IMO this is bad game design.

Repeat The Background

The background can be repeated until the boss is defeated. On the one hand this eliminates the need for suicide watching the boss, punishing the player with restarts or halting the flight at all. On the other hand it may puzzle the player when she's entering the level again.

Repeatable Patterns

This is Nordenfelt's solution to the problem. It has the advantages of a repeating background with a low loop-awareness factor. Take a look at the following image:

The background is built from segments. It is split into a level part and a boss area. The level part is a simple sequence of background segments. When this sequence passed by the boss area starts. This area consists of one or more segments which will repeat until either the player or the boss dies. So we can start an epic fight over an arbitrary period of time without hand-crafting an endless segment string.

At this point I can imagine two improvements. The first one is applying the composite pattern. This would improve the reusability of already defined segment sequences. It's more work on the programmer's side but may safe time during level design.

The second improvement is data-driven randomization. The background segments have to be like seamless textures. The top edge of each segment should be compatible with the bottom edge of at least one segment, be it the same segment or another one. The compatibility has to be defined somewhere, e.g. in a configuration file. This way the engine itself can decide which segments it should append in the boss area. Compatibility with multiple segments combined with randomness increases the variety of the boss areas.

Take a look at the following compatibility graph example. The segments are the graph nodes and the arrows are unidirectional edges. An arrow pointing from node A to node B means "A can be followed by B". Some nodes can be followed by themselves. Each node has at least one incoming and one outgoing arrow. Nodes without incoming arrows can only be used as starting segment. Nodes lacking outgoing arrows are end segments:

I'm wondering if there are further solutions to this problem. This list is just my own brainstorming result. Do you have an other idea how to solve the finite level problem? Let me know.

Cheers,
Thomas