Tech review - 2d fighting engines


Closed source. Very popular with community, but the maker is unreliable and rarely updates. (They don't even have a website.) Many games have been made with it but they are all free. No-one ever seems to have obtained a license for commercial distribution. Creating characters is tricky but there are plenty of tutorials and examples.


Some people claim this is a mod of Mugen, some claim it is a clone. There's no documentation and the author appears to only speak Japanese. It has source code which I think is written in Lua, and there are several forks made by different people, but no license info anywhere to say whether they are legal to distribute.


Open source side-scroller beat em up engine. Free for use in commercial games, works on Linux, Mac and Windows. Only has single author working on it and development is slow but is still alive. Technically looks pretty good. Could possibly be adapted to make a 1 on 1 fighter.

Paintown Mugen

Paintown contains within in a second separate game engine, which is an exact clone of Mugen. It doesn't seem to be used much so I don't know if it has reached 100% compatibility with Mugen characters, but it certainly works with the Kung Fu Man example. So if it works, this is probably better option for releasing a game than original Mugen.


Another open source side-scroller beat em up engine. Free, win/mac/linux etc. Under active development and has large community around it. Has actually been used to make a commercial game:

Unknown how difficult it would be to adapt it to make a 1 on 1 fighter.

Doom 2016 - what makes it so good?

The basic gameplay of Doom 2016 consists of 2 modes, which are alternated:


Unchanged from the original Doom and Quake games. Essentially it's a game of moving in a direction to avoid enemies while shooting in another direction while collecting powerups, like Robotron. The fact that is 3d rather than 2d does add the necessity of aiming up and down (although this wasn't even present in original Doom, which was just a 3d rendering of a 2d game). More recent FPS games feature hiding behind cover and automatic regeneration of health as essential elements of combat. The absence of these marks this as a throw back to the original Doom. (There is scenery which blocks line of sight and makes the combat more tactical, but hiding is not viable.)

However there is one new addition: the 'glory kill' system.


Combat is broken up by sections of exploration. These are made interesting by:

  • The graphical design and sense of place

  • The thrill of discovering secret areas

  • The game bonus/upgrade rewards discovered

Personally I find exploration less fun than combat. But the above items do bring it up closer, and it also fulfils a role of something to do which is a break from intense action.

The sugar that makes this is an AAA title:

  • 1st person perspective - increases immersion over top-down 2d shooters, requires more detailed textures

  • 3d graphics - latest tech is always impressive (at least while it is new)

  • Great music

  • Story. It's minimal so it doesn't get in the way of the action but the voice acting and plot are still good. Mostly it's back-story, discovering what already happened, so no need to worry about the player influencing events or creating a non linear story. Much of it is text based and can be ignored entirely if the player isn't interested.

There are also a number of other systems layered on top:

Collectable weapons

As in the original Doom, you collect more powerful weapons the further you advance in the game. This makes the player feel more powerful. The more powerful weapons have limited ammo, meaning they cannot be used all the time, so they also introduce new tactical decisions of which weapon to use which makes the combat mode more varied and interesting.

Variety of enemies

Each type of enemy behaves in a different yet predictable way. On encountering a new enemy type the player is forced to discover the necessary tactics to counter it. Then the player is attacked by multiple types simultaneously, requiring rapid thinking and deployment of the already learnt tactics, in more and more challenging combinations.

Weapon modifications

Most weapons have 2 modifications available. They are unlocked through exploration pretty easily, and the player is given the management decision of which modification to unlock each time. This gives the weapon 2 alternate firing modes, for a total choice of 3 different kinds of fire from each weapon.

Weapon modification upgrades

Each modification can be upgraded 4 times, providing unique bonuses when that modification is used. Modifications are purchased via points, so the player has to decide what is best to buy. The points are awarded for exploring secret areas, killing enemies (which is pretty much essential anyway, so these points are regular and automatic) and completing challenges (see below).

Player character stats upgrades

Each level contains one or two stat upgrade points. Usually they are pretty easy to find, so progression is mostly automatic, but the player is given the tactical choice whether to upgrade health, armor or ammo capacity.

'Rune' specials

Each level contains 2 runes, of which 1 is easy to find. After finding the runes a special challenge must be completed before they can be used. These special challenges take the form of combat in a special arena with special limits imposed, e.g. limited health, time, weapons, ammo. Once runes are found and unlocked the player must then choose which runes to equip - they each provide some bonus only while equipped. The player is limited in the number of runes he can equip at once, so he is forced to choose carefully, optimizing the combination of runes that work best together and perhaps changing the equipped runes depending on the situation and what challenges he is currently aiming to achieve. Examples… TBC


Each level has 3 unique challenges which give weapon modification upgrade points. Each weapon modification has one challenge to unlock the final upgrade. Each rune has one challenge to upgrade it. So at any one time in addition to winning the combat the player is trying to remember up to 3 or 4 current challenges to complete during the combat. Examples… TBC

Should you use a physics engine in your game?

In the real world, (almost) every object moves according to a set of laws known as Newtonian physics. If you want the virtual world of your game to feel realistic then it must implement the same laws. The easiest way to do this is to use a third party library such as Box2d. It will save you time and will probably be more accurate and efficient than your own physics code. However there are some cases that justify doing it yourself.

  • You want your game to behave like some classic game which did not use any realistic physics.

  • The physics of your game are Newtonian but the situations are very simple so you only need a small subset of the features of Box2d.

  • You want some Newtonian physics but you also want some physics that are unique to your game.

Let's see how Newtonian some common game control systems are.

  1. Constant velocity Movement (Space Invaders gun). You push left or right and it moves that way at constant velocity. You stop pushing and it immediately stops.

  2. Variable velocity Movement. As above but you can vary the velocity depending how hard you push on the analogue stick. Acceleration to the selected velocity is still instant so non Newtonian. Works for 2d as well as 1d movement.

  3. Newtonian 4 thruster. (Space taxi). Proper Newtonian physics with the limitation that your object is a square that cannot rotate. It has 4 fixed thrusters that can accelerate it up, down, left or right. Easy to implement because each thruster corresponds perfectly to an axis in two dimensions, and the screen is 2d, and joystick input is 2d. Gravity can also be modelled as a downward acceleration. Rather difficult for the player. Realistically in a vacuum speeds would be unlimited, which is problematic, and in atmosphere speeds would be limited by frictional forces, which you may not want to bother with, so you could just cut off thrust at a maximum velocity.

  4. Auto stabilized 4 thruster. As above, but player does not have direct control of the thrusters. Instead player uses analogue stick to input the desired velocity and thrusters are automatically fired to achieve this and automatically cut out as soon as it is achieved. Works well for 1d too.

  5. Brakes. As above, but the thrusters become more powerful when reducing velocity towards zero. This is realistic for an object in contact with the ground which could apply friction to slow down.

  6. Fast turns. Even with powerful breaks, a 1d character can feel sluggish when reversing direction. Probably because a 3d character could reverse direction without breaking simply by sharply steering. To emulate this we could skip velocity straight from +X to -x without going through zero.

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Tech review - Java web frameworks (for CRUD apps)

Java Enterprise

The first Java web framework was Java Enterprise (J2EE). This included a lot of stuff for distributed applications and didn't focus specifically on web applications. The web part was Java Servlets (the controller in MVC pattern) along with Java Server Pages (the view).

Note that Java EE was and is only a specification of an API: there are multiple implementations available from different vendors. You've probably heard of Jboss, Tomcat, Jetty, etc. I guess Sun wanted to encourage competition while providing standardisation, so you could take your app and deploy to any EE-compatible server, but possibly because the standard was the lowest common denominator agreed by all the vendors it was pretty clunky. Everything had to be configured with XML files before coding could even begin, which programmers found painful.

Thus Java was only really used on the web by large organisations who could mandate their programmers had to use it to be compatible with their existing Java EE applications.

This allowed crappy but easy to use dynamic alternatives like Perl and PHP to flourish.


The game changer was the release of the Rails framework for Ruby. Ruby is a dynamic typed language like PHP, so it is far slower and less safe than Java. But unlike PHP it is well designed, pleasant to use and it encourages automated testing to overcome the lack of safety. Rails used Ruby's dynamism and a principal of 'convention over configuration' to make it very easy to create web applications, specifically CRUD applications.

Rails single handedly made Ruby into a mainstream language and spawned a host of imitators in other languages (Django for Python, Yii for PHP).

Java couldn't emulate Rails directly because it lacked dynamic typing, so several different things happened. The first was, I think, Grails, a clone of Rails using the Groovy language. Groovy runs on the JVM and looks pretty similar to Java but with more dynamism. Grails is still popular today, although now it runs as a layer above the Spring framework. I think it is a good choice. although I'm not a fan of Groovy, you can write the majority of your app in Java. The only caveats are some parts will have to be Groovy, and since it runs on top of Spring it will never be faster and may be slower than Spring.


Which brings us to Spring. Not an easy thing to define! Spring began in the pre-Rails days as a dependency injection framework which was a reaction against the deficiencies of Java EE. As it grew it absorbed other popular frameworks, such as Hibernate ORM. It's popularity caused Sun to adopt many of Spring's APIs into future versions of the Java Enterprise API. Conversely, nowadays Spring is able to interoperable with and incorporate many of the Enterprise APIs. I think it bundles Jetty (?) inside itself too. So I'm not entirely clear on how to define the difference between them. Certainly you can do a Java Enterprise project and use different implementations other than those in Spring. If you do a Spring project then I think by definition your project is Java Enterprise because many parts of Spring implement Java Enterprise. And Spring is big. Many, many modules and sub modules make it difficult to generalise about.

Spring Roo

For a long time Spring was a competitor to Java Enterprise, not to Rails. The release of Rails did prompt Spring to attempt to drain their swamp of XML configuration files but Rails was still much more efficient at developing CRUD web applications. A couple of Spring subprojects have attempted to change this.

First was Spring Roo, which gets its dynamic magic from using AspectJ. This is good because you can stick to writing pure Java, while AspectJ quietly adds methods to your objects when you compile. It does scaffolding and lots of auto generation. It's part of the larger Spring ecosystem which is reassuring. So it's a good alternative to Grails without using Groovy. The only downside is that development and popular interest seem to have slowed to a crawl.

Spring Bootstrap

More recently they concentrated dev effort into a newer subproject, Spring Bootstrap. It provides a nice way of setting up a Spring project, making conventional 'opinionated' decisions for you. However this is only necessary because Spring had grown into such a huge maze of different modules that no one knew which ones they should install to get started! It doesn't seem to do any scaffolding so CRUD apps are still slow to get started. I suppose huge projects don't really care about scaffolding because the time saved is such a minimal part of their overall budgets and they don't need to iterate quickly anyway. But for me Bootstrap is still clunky compared to Rails.

The current version of Grails is built on top of Spring Bootstrap. Spring Roo is still in (slow) development and the next version will use Bootstrap. So I don't really see Bootstrap as an alternative to these projects - it's a lower layer in the stack. If you want to work at the top level then you wouldn't use Bootstrap directly, despite it's name.


Jhipster is another option for the layer-on-top-of-Spring-Bootstrap. It does even more configuration for you than Bootstrap so you can get started quickly, although it also gives you fewer options. It does scaffolding, but not just view templates on the backend, it generates a JavaScript powered front end too, using Angular JS.


If you want to stay outside the Java Enterprise / Spring ecosystem entirely then I don't blame you and there are many attempts at simpler Rails-like frameworks.

The most popular is probably Play. While Grail's secret sauce was the Groovy language, Play chose another JVM language, Scala, to get the ease of configuration they required. This worked pretty well and Play become very popular. Scala made a good template DSL for the views and you could write the rest of your app in Java.

Unfortunately the company that owned Scala was looking for a web framework too. They fell out with the developer of Scala's native web framework, Lift, and decided to buy out Play instead. They put a lot of money into marketing Play and its popularity increased, but they also took over the project and did exactly what they had done to Scala itself: over engineered it. When I tried to use it I found a beautiful system of thousands of parts working in harmony… Except some of the parts would regularly break, taking the system down, and not being a Scala experts I couldn't even tell which ones.

Ninja framework

Ninja seems like a version of Play that is actually used by in the real world and works. Still doest have scaffolding so is targeted at experienced developers. But it bundles an ORM, it has templates. I could happily use this for some projects. But we are now firmly in the realm of community supported projects - you have to be happy go without the reassurance of large corporate backing.


A very minimal framework. Doesn't have to download a load of jars like Grails and Play. Very easy to setup, very little to go wrong, but doesn't provide much. I think this would be good for someone who was already doing everything manually, e.g. PHP (without a framework). It doesn't have ORM. You can add ORM, but you can also just write SQL. It doesn't have HTML templates. You can easily add a template library, or you could just write HTML yourself. If you were doing a fully featured web app in Spark I feel you may as well use Ninja because you would end up adding all the stuff that Ninja bundles.

There of course hundreds of other frameworks I haven't mentioned, mostly small one man projects that that some people will love because they are so lightweight but personally make me feel like I'm having to reinvent the wheel.


Personally, what I want from an ideal Java web framework is:

  • Scaffolding to automatically generate CRUD apps
  • sizeable community
  • Enterprise level backing
  • reverse engineering of existing databases.

I don't like Play. Thus my recommendations are

  • Spring Roo (although stuck with old version because current version lacks DB reverse) and
  • Grails.

Jhipster is also very interesting if you want a fancy front end but don't want to learn whatever the latest hotness in JavaScript land is.