I wanted a kind of creepy giant worm for this one. In my head it would be somewhere between the giant sandworms of Dune and the real-world creepfest that is the Bobbit worm. It ended up having a healthy dose of H.R. Giger in there too! I’m currently calling it the ‘squirmer’.
Before starting on the art I thought I’d better knock out a quick prototype of worm-type movement as, if I couldn’t get that right in code, no amount of pixel-pushing would make things look any good. I spent some time pondering how to do this and in the end settled on a very simple skunkworks physics type approach (it’s probably less than ten lines of code) which, to my immense surprise, worked out incredibly well. There’s a really nice ‘slither’ effect to the tail motion which I really hadn’t predicted at all.
To get this effect I first move the head of the worm. I then iterate through each segment in turn (from the head downwards) and see if the distance to the previous segment is greater than a specified ‘joint length’. If it is I move it towards the previous segment by the appropriate amount. I then store the amount of movement as momentum so that the next frame each segment will move according to its stored momentum as well as being pulled by the next segment along. That’s the basic principle anyway.
Once I knew I had that pretty much nailed I started on the art. It didn’t take too long to get something that had the vibe I was looking for, what did take a long time for this one was animating it. The motion of the teeth itself was fairly simple but, for some reason, getting the mouth to look right around the teeth whilst it was opening and closing was tricky. I ended up having to make the whole head expand and contract slightly. For some masochistic reason I decided I should try making the whole mouth rotate (it just seemed as if it should do this) but the process of splitting everything out to get this to work ended up being extremely fiddly and time-consuming. I think it was probably worth the effort though.
I also spent a long time dithering over eyes. I went through multiple options as I felt it needed something ‘eye like’ for character, but everything I tried looked too cartoony or fish-like. At the end of the day it just seemed creepier without any eyes at all so I stuck with just simple antennae.
The tentacles at the side of the head also took a while. It felt like I needed something here and I tried a number of things (including extending jaws like the Bobbit worm) but none of them really did it for me. The tentacles seemed to work OK but, again, they were difficult and time-consuming to animate.
The segments didn’t take too long to get right though I was quite a while on the larger segments that ended up loosely based on the spiny shells from Super Mario.
To get the ‘glow’ effect for the segments I have a duplicate sprite in a much lighter colour palette. This is placed behind the ‘normal’ sprite and I vary the opacity of the ‘normal’ sprite’. It took a fair bit of tweaking before I was happy with this effect.
Once all the art and basic movement was done (around eight or nine days in) I could finally start on the attacks. There are three phases to the battle, in each phase only the tail segment is vulnerable so the squirmer must be destroyed one segment at a time until only its head remains. As each segment disappears (and when it moves to the next phase) its movement gets faster.
Stage One
The squirmer spits out eggs which, once they hatch, spawn mini carnivorous worms that move very fast and attack the player.
Stage Two
The squirmer uses an ‘extending mouth’ attack inspired by H.R. Giger’s Alien. These ‘extending mouths’ both attack the player and serve to defend the squirmer from the player’s attacks.
Stage Three
The ‘extending mouth’ attack become more powerful, the mouths are larger, more aggressive, and have a greater range. They also shoot laser beams.
The ‘extending mouth’ effect is based on the same code for the tail of the main boss but with adjustments made for tethering the tail to a fixed point. It took a fair bit of tweaking for this to look right but I think it seems fairly convincing now, or as close as I can probably get anyway!
I added a few a new audio effects, a sound for the squirmer’s teeth gnashing and rotating, firing eggs, eggs hatching, and a new laser sound which I’m particularly pleased with. As with all the sounds, these were created on the DSI Tempest.
Oh yeah, I’ve also finally added some bigger explosions and a special ‘boss’ explosion. I spent about a day on explosions alone as I’ve also created smaller ones to give more variety between the various enemies.
OK, I think I’ve gone on enough now. Next I have to go through the bosses (the first two mainly) checking a few things and making a few improvements – then I’m done with this and on to what should be the final major gameplay addition!
Dev Time: 11 days
Total Dev Time: approx 196 days
Skunkworks Physics – Tail Motion Proof of Concept
The Eyes Don’t Have It
Finally – The Art Pretty Much Done
Extending Mouth Attack Inspired By HR Giger
It's a Draw! The Final Battle...
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