The BitBull Blog

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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