Sabbatical Log: Retrospective

I took a sabbatical in November and set out to learn some game development. It’s been a month-and-change since I wrapped up, and now I’m looking back to reflect on my endeavor.


My auto-responder for the month I was out.

My auto-response while I was out.

Stack Overflow gives employees 4 weeks of paid vacation on their 5th anniversary, and an additional week each subsequent year — up to a maximum of 8 accumulated weeks. It’s the same as regular vacation in terms of scheduling, pay, and whatnot except that you must take a minimum of a month off at a time. It was a big year for sabbaticals at Stack Overflow; 13 people took them in 2018.

Before taking the time off, I knew I’d need a project to keep me entertained, and I decided I’d play with a kind of coding I’d never really done before — game development.

What did I do?

I built the very beginning of a A Link To The Past pseudo-clone, working from first principles. Besides actually blitting pixels onto the screen, I built everything: loading assets, collision detection, animations, room transitions, etc. In the end I had a game with one real room, a working enemy, a few interactable objects (doors, bushes, walls, and pits), support for room transitions, and a lot of half-way decent infrastructure.

What am I proud of?

I feel like I actually accomplished a lot, given how little I knew going in — I was just an enthusiastic reader on the subject, with a decent command of C#. More concretely, and with some distance from the original authorship, these are the parts I’m most proud of:

  • Hot reloading of assets
    • Sprites, animations, hitmaps, and room backgrounds can all be edited while the game is running and they’ll be automatically reloaded. This made me way more productive when it came to “creating” assets (i.e. chopping up LTTP screenshots and stitching them together).
    • For a real game, I would have built a bunch of tools for creating and previewing things, but hot reloads felt like a clever and cheap alternative given my limited time.
    • I did sprites on the 2nd day (which implicitly handled hit maps), rooms on the 7th, and animations on the 8th.
  • A focus on DEBUG performance
    • I spent most of my time in DEBUG builds since I was, well, building and debugging. Accordingly, I felt I had to keep DEBUG performance decent enough to actually run the full game.
    • Since wrapping up, I’ve come across discussions suggesting that some actual game devs share this sentiment, which is a nice bit of validation. Of course, they may not be representative of the game industry as a whole, but at least I’m not alone in my craziness.
    • I spent time explicitly working on DEBUG performance on the 14th and 15th.
  • A decent separation of concerns
    • I had never worked with the Entity-Component-System pattern, but found that it did a really good job of keeping code separated in a sensible way.
    • For example, both the knights and the player can cut bushes… but neither of those entities have any knowledge of the other. Generally, things “just worked” without nasty code.
    • I also kept rendering unaware of the rest of the game, which feels like an accomplishment.
  • Useful debug overlays
    • I implemented overlays for sprite bounds, collision bounds, collision polygons, sub-system timings, and render timings (including FPS). These were crazy useful for debugging, and frankly I should have worked on them even earlier than I did.
    • I implemented these overlays on the 12th, 13th, 14th, and 28th.

What didn’t I get to?

“The rest of the game” is the obvious answer, but I knew going in that there was no way I could build everything in a month. A few of the things that I had at least made notes to start on were:

  • A DeathSystem to handle death animations and dropping items when something dies
    • Right now the sword knight, as the only enemy, handles its own death animations, which is less than ideal.
  • A source of random numbers
    • Current code just uses a System.Random instance, but I’d like to implement a custom provider for a few reasons:
      • Guarantee of stability, so no matter where the code is running random numbers will be the same.
      • In the same vein, parallelism requires some changes so that random numbers are consistent in a frame even if the actual code runs at different times.
      • There’s a lot of fun to be had with manipulating RNGs in old games (check out the Luck Manipulation TAS videos), so a custom seeding paired with a simple algorithm can actually be a plus.
  • Recording gameplay videos
    • I kept the rendering code and logic code separate, in part to enable this, but never got around to it.
    • I captured all the GIFs in my posts with ScreenToGif.
  • Some system for positioning frames in an animation and/or multi-part entity
    • In a number of systems there’s a “glue” function that repositions various entities based on current animation frames, which is not great.
    • These relative positions shouldn’t be in code as constants, they should be loaded up as part of an asset.
    • I mulled over the problem for a while, but couldn’t come up with a nice generic solution… maybe there’s something in the literature I’m unaware of, or maybe I’ve structured my entities and animations poorly.
  • Automated rebuilding of asset/animation/etc. enums
    • I mentioned this on the 16th, and it only got worse as time went on.
    • Besides lack of time, my biggest worry was that I’d build something that wasn’t portable outside of my machine — always a risk when tweaking builds.

What do I regret?

  • Using a custom fixed point implementation for collision detection
    • It was an interesting exercise, and I’m not convinced that it couldn’t be done well, but I spent a lot of time on it for little gain.
    • I also had to spend a lot of time optimizing this code since, especially in DEBUG builds, it was thousands of times slower than just using floats.
  • I didn’t start on debug overlays soon enough
    • I assumed that test would cover most of the same ground, which turned out to be false.
    • A few days were lost because I hadn’t anticipated the need for debug overlays, making debugging a lot harder than it should have been.

Overall, I have few regrets, which feels indicative of a month well spent. That said, if and when I continue working on this codebase, I’m sure I’ll find more things to regret.

Where did I spend my time?

  1. Collision detection and related code
    1. I spent time on this during the 3rd7th, 9th11th, 13th, & 16th.
    2. This totals about 33% of my time over the entire sabbatical.
  2. Asset creation and manipulation
    1. This isn’t well accounted for in the actual posts, but most days I spent an hour or so doing something with assets. Oftentimes this was just scaling and making minor edits, but sometimes it was painstaking screenshot comparisons to figure out relative positioning between two separate assets.
    2. As a rough estimate, I spent about 12% of my time on this task.
  3. Debugging tools
    1. Primarily overlays, as documented in the 11th13th.
    2. A lot of ToString() implementations to make life easier in the debugger.
    3. This was probably also about 8% of my time.

Everything else took the remaining 40-50% of my time, which feels about right. Since I was mostly working on building up the infrastructure of a proper game, I don’t think spending half of my time on plumbing was a problem. Now, if I had spent a year or two on this project, that division of time would be problematic — I’d expect more time to be spent on the actual “game” part as development progressed.

Will I keep going?

I’d like to, which is a weaselly answer.

The value of uninterrupted time to devote to development is hard to overstate, and if I continue I won’t have that. So I couldn’t expect to be nearly as productive, which makes the whole thing less attractive — I’m one of those people who derives a lot of enjoyment from making tangible progress.

All that said, I’m going to try and spend a weekend every now and then plugging away at the LearnMeAThing codebase. I may even keep notes and blog about it occasionally.

Where’s the code?

I can’t exactly publish the whole project, since it’s full of Link To The Past derived assets. I’m also not all that interested in really open sourcing it, because it’s a learning project for me I wouldn’t accept pull requests or handle issues. That said, I like the idea of folks learning from my examples-and-or-mistakes: so I put together a GPLv3 one-time dump of just the code.