Category Archives: Jetboard Joust

Jetboard Joust Devlog #81 – On A Roll!

In the late 1970s, when kids played with proper toys rather than tablets and smartphones, there was this marvellous toy called ‘BigTrak‘. I always wanted one, but they were way too expensive to buy and probably cost around £10k per year in batteries. I’m sure the reason there’s so many SUVs on the roads today is that all these 40-something-yr-old men are buying them as some kind of mid-life BigTrak substitute. I still think the BigTrak design looks pretty cool even today.

This enemy, the ‘crawler’, was very much inspired by BigTrak, but it wasn’t just a nod to seventies nostalgia. At the moment gameplay seems to gravitate very much towards the top of the screen and I wanted something other than pickups to take the player closer to the ground and amongst the buildings. A ground-based enemy seemed the logical choice to do this.

Usually I’d work on the art first but in this case I thought I’d run a few code tests first to see if the ‘tank’ type enemy I had planned had any kind of hope of succeeding. Maths is not my strong point, and as this vehicle would have to perform the impossible feat of traversing vertical slopes and 90° changes of gradient I needed to make sure it wasn’t going to look like arse before I wasted loads of time on the art.

To my surprise my initial tests worked very well. There’s no ‘physics’ at play here, the wheels (working independently) simply traverse the outer edge of the terrain in the most basic way. I then work out the angle between the wheels (i.e. the axle) and place and orientate the chassis based on this. It’s not physically ‘correct’ by any means as the distance between the wheels changes depending on the terrain but, as it’s performing impossible feats anyway, I didn’t think this mattered – I could get away with a telescopic axle! In the final version I added something to make the wheels roll more nicely around corners but other than that I stuck with my first approach, I made a couple of attempts to make things more ‘realistic’ but both ended up looking worse than the original.

Satisfied that I could make this work I then began work on the art. There were two keys things I had to bear in mind here. Firstly, the design needed to be such that the distance between the wheels could change without looking ridiculous as described above, and secondly that the vehicle could travel in either direction. I think you can get away with simply flipping sprites for left/right when they’re small but with larger sprites like this that approach can look pretty ropey.

At first I was working on a ‘tank’ type idea that was similar to BigTrak. I spent several hours on this but wasn’t happy with anything I came up with. Everything looked too clunky or too much like a motorbike. So I started experimenting with some radical changes and in the ended settled on a kind of armoured ‘push me/pull you’ design that I felt worked much better. It’s a complex affair though, the final unit comprises eleven different sprites, so getting these all lined up and positioned correctly was a very fiddly business!

Getting the guns to track the player was also fairly tortuous as one has to consider the rotation of the vehicle as well as the previous rotation of the gun to make things work smoothly. People with more of a maths brain probably find this stuff easy. I don’t, but I got there in the end.

The AI wasn’t simple either. For individual vehicles it’s pretty straightforward, but when they appeared in batches I was getting issues (as with the Squocket enemy) of them overlapping too much. In the end I created a ‘hive mind’ class that acts as a controller for a bunch of vehicles. This class works out the ideal positioning of each vehicle and then the individual vehicles track to this position.

Lastly I have the pilots of the vehicle man jetboards and make a last-ditch attempt to attack the player when their vehicle is destroyed. There’s a specific class for this type of enemy too (I’m calling it the Kamikaze) but it’s pretty much one of the basic minions with tweaked parameters.

EDIT: Aaarggh – I thought I was done but whilst working on some screengrabs for this post I ran into a hideous bug to do with the world wrapping (remember I talked about that here?). I was getting all sorts of problems caused by the vehicle wrapping at a different time to any of the buildings it was in contact with. Very difficult to find a solution for this so in the end I’ve settled on a bit of a hack whereby the vehicle stops moving if it’s very close to the edge of the world. This seems to work OK and I don’t think it will be too obvious in practice.

So, the most complex enemy to date but I’m pleased with the end result. I think I only really need a couple more like this and I can move on…

Dev Time: 4 days
Total Dev Time: approx 166 days


Abandoned Art Direction – ‘Tank’

The Finished Design – ‘Push Me/Pull You’

Guns Tracking Player And A Nicer Rolling Action Round Corners

Using A Variety Of Weapons To Dispatch Two Crawlers (Enlarged 150%)


Jetboard Joust Devlog #80 – Squid’s In!

This latest enemy was inspired by the rockets in ‘Scramble‘, the other seminal side-scrolling shooter (along with ‘Defender‘) that defined the genre for me in the early days and paved the way for the likes of Nemesis, Salamander, Gradius, and all that came after.

I didn’t want to have bog-standard rockets though. Every other enemy in the game is humanoid to a degree (when I do have spaceships etc there’s an obvious humanoid pilot). I feel this imbues them with much more personality – so I began working on ways to ‘humanize’ a rocket.

I was thinking about Tomohiro Nishikado’s original sketches for ‘Space Invaders’, which were in part inspired by aquatic life like jellyfish and crabs, when I hit upon the notion that giant squid are not only very rocket-like in form but also have great Cthulhu overtones which links in to some of the other art in the game (the Mutants in particular).

So I decided to name this enemy a ‘squocket’ – a cross between a squid and a rocket. What I didn’t consider though was how much of a bastard those tentacles would be to animate! The main animation took me the best part of a day and is probably the most fiddly piece of pixel art in the game so far. I’m pleased with the end result though, I decided to make the animation symmetrical because it was simpler and also felt more ‘Space Invaders’ that way.

There’s also an idle animation as the squockets wait for the player to approach. This is much simpler but still took a while finding a nice way to make it loop. In the end I decided on a five frame ‘back and forth’ animation for this.

The movement of the squockets was pretty easy to code – I work out the angle between the squocket and the player and ‘lerp’ towards this. What I was finding was that multiple squockets began to overlap after a while (often almost exactly aligning) which looked pretty daft, so to counter this I started polling the player’s position only around four times a second and adding a certain amount of randomness to the polling time, this has pretty much alleviated the issue though I may work a bit more on this – maybe adding a ‘ram’ attack or something.

I also had to deal with squockets becoming ‘stuck’ on the side of buildings if there was a building between them and the player. To solve this I have the squocket rotate upwards if it hits the left or right of a building and to a horizontal position if it hits the top of a building. This seems to enable them to find their way around pretty well. I did play around with a ‘lookahead’ sprite placed a certain distance in front of the squocket and using this to navigate around buildings but this approach almost worked too well (they would avoid buildings so effectively that the player could hide too easily).

Lastly I gave them the ability to fire (I actually re-use the bullets from the original ‘spreader’ weapon) and added a simple ‘tell’ animation prior to firing.

Dev Time: 2 days
Total Dev Time: approx 162 days

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The Main Squocket Animation

Squockets At Rest

Jetboard Joust Devlog #79 – Space Invaders

In my last post I wrote about maybe recycling the old ‘Evil Mother’ enemy into something based on the classic ‘Space Invaders‘ aliens, and that’s exactly what I’ve ended up doing!

I like the idea of including a few homages to the classic arcade shooters of yesteryear in Jetboard Joust, and as ‘Space Invaders’ was really the granddaddy of them all it’s an obvious choice. I wasn’t sure whether the formation/movement of the invaders would work within the horizontal/scrolling format of Jetboard Joust but, with a few tweaks, it actually seemed to work out pretty well.

It wasn’t too tricky to code either. I was worried that get the whole batch of invaders to move together around buildings and stuff would be a pain but it was pretty straightforward in the end.

What I do is move all the invaders as a batch rather than treating them as individual sprites. Collision detections are still handled individually and, when an invader collides with a building, it sends a message back to the batch telling it to change direction. When the batch is initiated I make sure it doesn’t take up more vertical space than the space between the highest building and the top of the screen so I know it’s never going to get stuck.

Probably the trickiest thing was deciding how to treat a batch of invaders when attacked by the ‘Gravity Hammer‘ weapon. Moving the whole batch at once would just look dumb so I needed a way of having individual enemies break formation when hammered and then return to the appropriate position once they recover.

To achieve this I have a property for each invader that stores its location within the batch separate from its position on screen. If the invader is forced to break formation it is relatively simple for it to return to its batch position. Though it wasn’t strictly necessary I also decided to have individual invaders track horizontally with the batch even when hammered (so only their vertical position is displaced). It just seemed to look better this way.

In keeping with the original I have the invader’s speed and rate of fire increase as individual invaders are destroyed.

Dev Time: 1 day
Total Dev Time: approx 160 days

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Admit It – You’ve Always Wanted To Play ‘Space Invaders’ With A Flamethrower!

Using The Plasma Rifle To Dispense With A Batch Of Invaders

Jetboard Joust Devlog #78 – Return of the Evil Mothers

Too long since the last update. Had a lot of shit on – decided to fight a parking ticket issued by one of those fascist private parking companies and it ended up in court. I beat the tossers but it took so much time preparing the defence and everything I’m not sure if it was worth it, just did it on principle really as I don’t like scammers or bullies. Turns out these scumbags didn’t even have the right to operate on the land on which the ticket was issued in the first place!

Anyway, back on topic, the first major ‘new’ enemy is actually an ‘old’ enemy redone, but I don’t think there’s any shame in that. If you’ve been following this for some time you may remember the ‘Evil Mother‘ enemy. Well, I’d come to the conclusion that this enemy just wasn’t big enough and would work better (and make more sense) as some kind of mini mothership that spilled out its occupants when destroyed.

So I spent quite some time designing a kind of ‘bathysphere’ type craft. It’s actually several different sprites in one, the ship itself, the pilot, the ‘antennae’ on the top which acts as a weapon, plus the various lights. I’m pretty pleased with the result though a little worried it looks a bit too ‘2D’ and could do with some more shading or something to make it appear more ’rounded’.

I also increased the size of the enemies that spill out when the craft is destroyed and spent quite some time working on a much improved bullet that tracks the player’s movement in a similar way to the Limpet Mine. There’s also a ‘tell’ that the ship is going to fire as you can see the antennae at the top charging up.

The shaking effect is achieved by applying an offset to the ships position each frame. These offsets are always evenly distributed and chosen at random so it’s a very predictable type of brownian motion.

I think I’m going to use the original enemy design as more of a ‘swarm’ type enemy with a movement type that’s an homage to the original Space Invaders!

Dev Time: 3 days
Total Dev Time: approx 159 days

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Jetboard Joust Devlog #77 – Keeping Your Enemies Close…

Been working on some new jetboarding enemies over the past few days, so around a day of pixel-pushing and a day of coding with the extra half day fixing bugs caused by the new ‘world wrap’ technique I described in my previous post. I’ve also been rejigging my sprite sheets so the art used for the jetboard and weapon attachments is duplicated on the enemy sprite sheet (fewer spritebatch calls to the GPU needed and should also make things easier if/when I add alternate colour palettes).

Fortunately new jetboarding enemies are relatively simple from a code point of view as a much of their ‘personality’ is defined by tweaking parameters already present in the AI. I also have a fairly decent template for doing the animations now too. Here are the new enemies that have been added, names are just codenames really so may well change…

1. The Master Minion
This is really just a bigger, stronger, and slightly more dangerous version of the omnipresent ‘minion’, the game’s cannon fodder. They’re quicker to snatch your babies away and mutate too!

2. The Ninja
Small, fast, light, very aggressive, but also pretty weak. This guy is very dangerous and performs a ‘pincer movement’ around the player really frequently making him a tough opponent to deal with.

3. The Aggressor
This guy is strong, fairly nimble, and very aggressive when you rile him but he’s actually pretty dumb and will let you sneak up behind him and get in the first shot. A bit like some of the knights in ‘Dark Souls’ (well, kind of)! You can tell which way he’s facing by looking at the scanner. This enemy required some custom AI work.

4. The Thug
This guy is very big and strong and takes a lot of ammo to dispatch. He’s pretty slow though, and not the brightest lamp on alien street either. I was particularly pleased with how the art for this one worked out.

5. The Snatcher
All this guy cares about is stealing your babies and trying to mutate. It’s like he’s a kind of half-mutant already and is desperate to finish the job. He’s a bit of a coward and will actively try and avoid the player unless directly engaged – watch him though, as he’ll snatch away your progeny and mutate really quickly if you don’t keep an eye on the scanner! This enemy required the most custom AI work.

This brings the total of enemy types to 12, I think I’m going to try and bring it closer to 20 and want to add some ‘miniboss’ type enemies with much larger sprites. few more smaller ones to do yet though…

Dev Time: 2.5 days
Total Dev Time: approx 156 days

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The Master Minion – Upgraded Cannon-Fodder

The Ninja – Fast And Dangerous

The Aggressor – You Won’t Like Him When He’s Angry

The Thug – Strong But Easily Outwitted

The Snatcher – A Devious Coward

Jetboard Joust Devlog #75 – A Farewell To Arms

At last – weapons are done!

This past few days has been 50% pushing pixels and 50% working on shaders for the weapon effects I decided I wasn’t really happy with.

For the grenade launcher I designed a new grenade as I felt the old one was really pretty shite in the cold light of day. Instead of a more ‘traditional’ type of grenade I went for something that looked a bit more sci-fi and this seemed to work better right off the bat. I probably only spent about half an hour doing it (if that) which is ridiculous compared to the amount of time I spent tweaking the previous version. You can see the original here.

For the plasma rifle I felt the old effect was too overblown so went for something rather simpler using a shader rather than particles. The new effect is just one sprite drawn with a custom shader that renders a fade with a low ‘bit depth’ to look pixelated. It also draws small gaps between the (imaginary) pixels. I much prefer the result and it’s considerably more akin to the player’s weapon in Defender which is what I was going for. You can see the original here.

The particle storm (originally ‘spreader’) is a weapon that’s caused me much pain and grief. The original effect (which you can see here) wasn’t bad at all but I felt it seemed a bit clunky compared to the other weapons, too pixelated or something. The new version adds a new sprite at each frame which is drawn with a custom shader to give a blend effect, there’s also some particles that decay very fast at the front of the ‘beam’. To be honest I’m still not 100% satisfied with this but I think it’s much better than the original. I’ll probably come back to this (yet again) at a later date but for now I’m parking it. It’s in the right ballpark now at least.

The pixel-pushing I had to do was drawing version of all the ‘futuristic’ weapons for the upgrade screens. I really don’t have clue what I’m doing with this type of pixel art and the process often feels akin to a monkey trying to write Hamlet by bashing out random keys on a typewriter. It might have been easier if I’d have sketched the weapons out by hand first, the fact that I had no real point of reference for what they should look like made things even harder!

I’m pleased with the end results though I think. The particle storm is maybe still a bit weird (that weapon’s been a bastard to get right all round). I’m also a bit undecided about the pulse cannon – it looks fairly badass in most respects but there’s something about it that reminds me of whale(!) which I don’t really like.

I’m particularly pleased with the gamma ray and sonic boom but in some respects these were the easiest as I was referencing common retro sci-fi tropes.

Dev Time: 3 days
Total Dev Time: approx 152 days

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The Newly Designed Grenade

The New, Simpler, Plasma Rifle Shader Effect

The New Particle Storm (Why Is This One Such A Bastard To Get Right)?

Pixel Art For All Weapon Upgrades

Jetboard Joust Devlog #74 – Hit Sounds!

For the past few days I’ve been completing the audio for the new ‘futuristic’ weapon set. It’s been quite a task, only eight weapons but over thirty sound files in all including variations.

The process has been the same as for the bulk of the Jetboard Joust audio. I do everything using hardware, most of which is analog, and then some final processing (limiting, eq, compression) in Logic Pro. Very occasionally I’ll add some additional fx using plug-ins (pitch-shifting and saturation were used here), and sometimes I’ll end up layering two different sounds in Logic when I feel a sound is ‘almost there’ but just requires a little extra.

Once the sound is done I then import it into the game to get the level balance right and then either back to Logic for some final tweaks or, sometimes, right back to the drawing board if things really aren’t working in context. Though I was always watching a GIF of the weapon in question when designing, sometimes when you hear it in-game it just doesn’t work. Sounds that are overly reliant on bass frequencies are often particularly problematic as they can clash with the background music and are low in perceived volume (see Fletcher Munson).

Overall this process seems to work well for me. The hardware is fun to tweak, has tons of analog character, and seems to provide the right balance of flexibility and restrictions. If I tried doing the same thing in the digital realm with something like Native Instruments Komplete for example (which I own) I would just get bogged down with all the options.

The key piece of hardware I’m using for this project is the DSI Tempest – a six voice, multitimbral synth/drum machine. It has two analog and two digital oscillators. For this project I’m tending to restrict myself to the analog oscillators but will sometimes use the digital ones for noise samples.

For the hardware fx I’m limiting myself to the four aux sends on my mixing desk. I use a Roland RV-1000 digital reverb, a JHC DX-77 digital delay (both picked up really cheap on eBay), and an Echolution2 Ultra Pro delay pedal. I have a distortion unit on the last send which I switch between the awesome Malekko B:Assmaster and a Waldorf 2-Pole analog filter.

I don’t use any bitcrushers or anything like that. I’m going for a sound that’s pretty much a full-on aural assault in the way I remember Defender being but trying to create that vibe through distortion and the overall timbres used rather than restricting sample rates and bit depth. The result is a kind of hi-fi/lo-fi hybrid.

Dev Time: 3 days
Total Dev Time: approx 149 days

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Some Of This Gear Was Abused, None Of It Was Harmed

Jetboard Joust Devlog #72 – Stick To Your Guns!

For the penultimate (hurrah!) weapon I decided to go for a heat-seeking ‘limpet mine’ as I don’t currently have anything like that in the game. Not sure if this counts as a ‘conventional’ or ‘futuristic’ weapon as it’s really somewhere between the two.

Most of the coding was done on this before Christmas and I am currently suffering from a heavy cold so excuse the brevity of this blog entry!

It wasn’t that tough a weapon to put into action, for the motion I work out the ideal vector between the mine and its target and then ‘lerp‘ the mine’s horizontal and vertical velocities towards this value (with a set maximum ‘acceleration’).

I found that sometimes mines were getting stuck against the edge of buildings if the nearest target was on the other side of a building, so I implemented a very simply AI that moves the mine to the top of a building if its path is blocked. This seems to work fine and gives pretty amusing results in some scenarios.

The other simple AI I added is a check to see if a target already has a mine attached. If it does, and the HP level of the target is low enough to be knocked out by it when it explodes, further mines will seek alternative targets to prevent them being wasted. This is pretty satisfying in-game as you can just fire a bunch of mines into a swarm of enemies and trust them to find their individual targets.

Actual development of this weapon took about a day and a half, the extra time was spent improving my mother-of-all-geometry-shaders to draw triangles, six and eight pointed stars and add decent-looking fades for all these various shapes. The six-pointed star is used when the mine explodes and I will definitely be using these elsewhere in the game too.

Oh yeah, enemies with limpet mines are rather too dangerous at the moment! I am going to have to implement some kind of enemy-specific ‘pause and reload’ functionality for all the weapons.

Dev Time: 3 days
Total Dev Time: approx 143.5 days

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(Vaguely) Intelligent Selection of Target

Not Getting Stuck On Buildings

A Sticky Situation

One of the New Geometry Shaders – Six Pointed Star

Jetboard Joust Devlog #71 – (Black) Hole In One!

This was the first weapon that I really didn’t have much of a clue what I was going for when I started it and, ironically, it’s probably turned out to be the one I’m most pleased with!

When I set up the placeholder for this one ages ago it was called ‘Storm Bringer’ and I had an idea it was going to involve some kind of ‘particle storm’ type effect, a bit like those fireworks you get that fire out a ton of different sparks that go off in different directions.

However, I’ve already changed the ‘Spreader‘ weapon to be called ‘Particle Storm’ and, as that now does something very similar to what I intended this weapon to do, differentiating this weapon proved difficult.

I tried a series of variations with a bunch of particles moving in a constrained and stuttery ‘Brownian Motion’ type manner but this all looked shite and, to be honest, given that I’ve done so many of these weapons now I was beginning to feel like I was running out of ideas and motivation.

Then came a random source of inspiration. In my very skunkworks home studio I have a rack for audio gear that I’ve cobbled together over the years from various shitty pieces of Ikea furniture and stuff. In an attempt to make this more uniform (as nothing matched and my workmanship was so terrible) I covered the entire piece with Jack Kirby art from a bunch of old Spiderman and Fantastic Four comics I had as a kid.

On one small section of this there’s an image of a character disappearing into a kind of black hole, the image is drawn in negative and looks really striking. I had vaguely considered a weapon called ‘Black Hole’ (though I was worried it would be too similar to the ‘Sonic Boom‘) so I decided, largely out of desperation, to try switching the particles I was using to very dark circles with a light outline. I thought this would look ridiculous but, to my surprise, it actually looked kind of cool!

It’s not a single black hole though, so I hit upon the concept of a weapon that fires a series of mini black holes that suck the life force from enemies. Stephen Hawking would probably turn in his grave but I liked the idea. I’m calling it the ‘Black Hole Blaster’ which, thankfully, just about fits in the space I’ve reserved for weapon names in the HUD!

I worked on this ‘negative space’ effect some more, adding a layering system to my particle code so that I could draw all the white outlines ‘behind’ the black circles, this gave the effect of a unified black mass with a white outline which looked much better than a bunch of circles overlaid. As usual there was a lot of tweaking and messing around here (I didn’t really have any point of reference for the effect I was trying to create other than that one comicbook panel) but I’ve ended up with something I think works.

There’s five layers of particles in the final version two sets of black circles with light outlines (one smaller than the other) and the concentric circles you see overlaid which (I think) help to give the impression of some kind of black hole rather than simply black smoke. It was difficult to get these concentric circles subtle enough to suggest ‘black hole’ without overwhelming things, I had to do a lot of messing around with the frequency and distribution of them. It’s possible that I’ve erred to much on the side of caution and could do with a few more of them. It does look a bit like some kind of weird satanic flamethrower but I don’t think that’s necessarily a bad thing!

Lastly, whilst working on the collision detection (which was very straightforward) I thought it might be a nice touch if these mini black holes exerted a small gravitational force, actually sucking enemies towards them. This was pretty fiddly to code, and my initial version was ludicrously powerful, but it did seem to work and help to differentiate this weapon nicely from some of the others.

So I think I’m pretty much done with this one now. I’m really pleased with it, both in the way it looks, but also for the fact I’ve never seen a weapon quite like it in any other game (though some smartarse will no doubt point one out to me)!

Only two weapons left to go!!

Dev Time: 2 days
Total Dev Time: approx 140.5 days

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The Jack Kirby Panel That became My Inspiration

An Early Draft Of The Weapon

The Final(ish) Version

Too Much Suction!

Black Hole Dogfight!

Jetboard Joust Devlog #69 – Boom Boom, Shake The Room!

This latest weapon is called the ‘Sonic Boom’ and I had a fairly good idea of what I wanted it to look like visually before I started. Something akin to radiating circles but not so regular in feel.

I remember seeing something as a kid in a book about optical illusions (we had no Internet then, kids) that always stuck with me – it was an image comprised of two sets of concentric circles, the centres of which were slightly offset. It made your eyes go funny and that was a good thing.

So I started on that basis, by updating the geometry shaders I discuss here to include multiple sets of shapes that are offset by a certain amount. It took quite a while to get this working in a way I was happy with (and to structure the HLSL in a way that was sensible and would allow me to add other shape types easily), but the result was pretty satisfying if nothing like the effect I set out trying to achieve!

I realised there was just too much being drawn in the shader so I set about adding some different paint modes to vary the effect created. As well as the original ‘OR’ logic (if a pixel contains a shape it’s drawn) I added AND, XOR and NOT modes that react differently, particularly where shapes overlap. For the AND and NOT modes I allow a number of overlaps to be specified, with AND any pixel that contains >= the number of overlaps is drawn, with NOT and pixel that contains < the number of overlaps is drawn.

By combining these modes and a lot (and I mean a lot) of tweaking I was finally able to achieve the type of effect I'd set out to create. The final version consists of two overlapping geometry shaders for the bulk of the effect, particles around the barrel of the weapon, and a smaller 'negative' geometry shader also around the barrel of the weapon.

As with most of these weapons, the actual mechanics of it were pretty straightforward to program. It acts really like a kind of RPG that must be 'charged' before being released, if anything it's even simpler than the RPG because I'm allowing this one to travel through buildings (I'm not sure if I'll keep it like that or not, it does seem a little weird).

I did also have to update the enemy AI to allow them to cope with a 'charge and hold' type weapon but that was pretty easy. The audio design for this one's gonna be fun!

Dev Time: 2 days
Total Dev Time: approx 136.5 days

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First Stab At Updated Geometry Shader

Adding Different Paint Modes To The Geometry Shader

The Final Sonic Boom Effect

Adjusting Enemy AI For ‘Charge And Hold’