Here’s a video of the latest build of Professor Sinister:
The most obvious change is the inclusion of the score/level/etc indicators at the top of the screen. Those are implemented as tiles in one of the GBA’s 4 background layers, giving us one layer for the text, one layer for the platforms, one layer for the parallax background, and one spare layer.
It wasn’t really noticeable in the previous video, but there was a little flickering at the top of the screen in both the sprites and the background tiles. It turns out that my belief that there was no performance work to do in the game engine was incorrect. Representing the vacuum tubes and power packs as “game objects” (essentially a data structure representing a sprite) instead of just inspecting tiles in the level data meant that the game had to iterate over them all when testing for collisions. That taxed the GBA’s tiny brain just a little too far.
The game just about got away with it until I decided to support larger levels with larger quantities of collectible items (demoed in the video above), at which point the horizontal tearing was too awful to ignore. I had to rewrite the egg/chicken feed code in the SZChuckie library, and then update both the Professor Sinister and the Chuckie Egg front-ends to match. Larger levels will let me take advantage of features of the engine that Chuckie Egg can’t use, such as arbitrary numbers of vacuum tubes, power packs, elevators and robots.
The game now has a “Simian Zombie” logo screen and horizontal scrolling text on its title screen (but it’s really inefficient so I’ll probably rewrite it), and a functioning “get ready”/“game over” screen.
I rewrote the way that the duck moves. The old code was pretty nasty and only managed to move the duck in one of 8 directions (horizontal, vertical, diagonal), whereas the new code uses vectors (correctly this time) to calculate a more direct route to the player. I still haven’t come up with a new design for the duck, though, so it’s not visible in Professor Sinister yet.
Speaking of design, here’s some more detail on Professor Sinister’s graphics. I originally wanted the robots in Professor Sinister to look like something from a 1950s sci fi movie: clunky and boxy, and covered in flashing lights. Their bodies would be separated into two distinct parts, so that when they changed direction the bottom half would spin 180˚ before the top swiveled around to match. I eventually ditched that idea because it would slow down the gameplay and would require far too many changes to the Chuckie Egg library.
I refined the pool of robotic inspirations down to just two: the robots from “Wallace and Gromit” and “Forbidden Planet”. In the former, I liked the little wheel that the robot scoots around on. In the latter I liked the bulbous design, segmented arms, and pincers.
The first design I came up with was very similar to the version that ended up in the game:
It was taller and thinner, however, so that when I tried transferring it into Aseprite I quickly realized that it was entirely the wrong shape. The robot was too tall for the 16x16 sprite and didn’t take up enough horizontal space. At that point it seemed that I’d have to ditch the design entirely, because trying to squash the robot into a wider, more cylindrical shape (from Robo to Mobo) didn’t work at all.
I gave up on the robots and switched to Professor Sinister. I was aiming for a cross between Dr Robotnik from “Sonic the Hedgeghog” and Dr Wily from “Mega Man”. Most of what I draw ends up looking like something from “The Far Side”, so that’s where I started. I knew I wanted thick, opaque glasses, a round head and body, and a lab coat, but the lab coat never looked right and neither did the body:
In pursuit of new ideas I briefly toyed with the idea of making the professor female, but I didn’t get very far with that. Instead I tried out an egg-shaped head (referencing Chuckie Egg) with feet directly attached to it, like Dizzy, and it looked pretty good:
Once I had a sketch to start from, getting the character into Aseprite was easier than I’d expected. The only feedback I got on the sprite was “it looks too much like an egg”, so I added a ring of white hair around the top of his head to hide his eggy-ness.
“Rick Dangerous 2” provided much of the palette for the professor. Its graphics are wonderfully cartoony and vibrant. I’ve always wanted to make a game that looked like Rick 2. Borrowing colors from its palette seemed like an obvious first step.
With the professor finished I realized that I could keep the egg theme for the robots. I took the egg shape, flipped it upside down, and suddenly the design worked:
It took some flipping between Aseprite and Acorn to get the sprites into a form that Grit could convert to C code. Grit of course utterly failed to produce correct palettes. I had to figure out which index Grit had assigned to each of the 60 or so colors used in the game and the set up the palette in code. Each minor edit to the graphics completely changed the layout of the palette, meaning more manual palette layout. I later discovered that although Grit can’t produce a palette from BMP, PNG or PCX files, it will correctly convert palettes from GIF files.
Testing out the graphics revealed a problem with the professor sprite. In Chuckie Egg, Harry’s feet are precisely aligned with the collision area between Harry and the floor. It’s possible to be pixel-perfectly accurate in moving him to the edge of a platform. In the new graphics I’d made the professor’s feet much larger and had completely lost that accuracy. I had to redraw the feet to line up with Harry’s.
The ladder uses some of the palette from Rick Dangerous 2, as do the background tiles (which were heavily influenced by some background tiles in one of the Rick games). The platforms are also similar to platforms in Rick 2.
I created the vacuum tube and power pack tiles, and the elevator sprite, entirely from scratch. I had a look at a couple of vacuum tubes on Google for inspiration, but otherwise I didn’t have any reference for these graphics.
As for the duck, I had a couple of ideas: a sphere (in reference to “Impossible Mission”) or a demonic robot face (like “Sinistar”). Then I remembered that it needs to be roughly the same shape as the duck or the collisions won’t work correctly, so I’m now considering some kind of robot pterodactyl thing.
The todo list doesn’t seem to be getting any shorter:
- Add a title screen bitmap.
- Write music for the title screen.
- Write music that plays when Sinister is killed.
- Create new graphics for the duck and its cage.
- Replace the sound samples.
- Add a high score screen.
- Replace all level designs.
- Add an attract mode.