Just Below the Surface

2026-08-13

For js13k 2026, theme "UNICORNS AND RAINBOWS".

Design

• Randomly-generated treasure hunt.
• Setting is tiny tropical islands.
• Locate treasures by summoning a rainbow segment.
• Treasures are unicorn bones. You're an archaeologist, assembling the unicorn's skeleton.
• Top-down view.
• Multiple items:
• • Wand. Summon rainbow.
• • Shovel. Dig.
• • Keys. Drive boat. Not equippable.
• • Metal detector. Bonus: Identifies metal things eg gold.
• • Magnifying glass. ''
• • Divining Rod. ''
• • Geiger Counter. ''
• • Compass. ''
• • Map. Automatically reveals areas you've visited, the rest are murky. And marks treasures you've dug up.
• • Machete. Cut thru foliage.
• • Bomb. Open caves.
• • ...For js13k, ended up with just Wand, Shovel, and Compass. You have them all from the start. Compass is entirely passive.
• At its most basic, we only need Wand and Shovel.
• Helpers that can incrementally mark undiscovered treasures on the map. Maybe only indicating which island?
• How about fishing off the boat? Find bones out in the open water too.
• Deluxe CD-ROM Edition! Just as a gag.
• • Must be larger than 1.44 MB (otherwise it would be the Deluxe Floppy Disk Edition).
• • If it tops 5 MB (4816896 exactly), it will be my largest game ever. I'd get a kick out of that.
• • Ideally larger than 13 MB. But no more than 700 MB, as if that were possible.
• • Build and measure exactly the same way as the js13k edition, no cheating.
• • Spurious data not allowed. Everything we include has to be used and has to be reasonable. Again, no cheating.

Tech

• Straight JS. No Egg, Wasm, Shovel, just write from scratch in JS.
• Copy Egg's minifier? Or whatever. Start with serving directly only, and ensure it always works that way.
• • ...Using Egg by reference for build. Helpful, because we also have a native tool that borrows Egg bits.
• Sound effects: Assume we'll have a set of enumerated sound effects. Something that translates neatly into WebAudio.
• Music: Start from MIDI and assume we'll pack that into something tighter. No pitch bend. Maybe no FM? ...see below
• Control:
• • Dpad to walk. In boat, it moves the same as walking.
• • Action, Inventory, and Pause buttons. ...nixed pause
• • Hold Inventory button and you can L/R to change the equipped item. Full inventory visible at all times.
• • • Did it this way but in hindsight it's overkill. We only have two equippable items. Could have just mapped one to each button.
• • • But don't change it, because I expect the Deluxe CD-ROM Edition will have a richer set of equippables.
• World map is generated as a huge grid.
• • Should we make one map per island, and not record anything for the vast waters between?
• • • NO. Don't need the extra complication, and memory is cheap.
• • I want caves too. So there's outer world and multiple inner maps.
• Framebuffer size? Sprite size? ...240x135 and 16x16. Can freely adjust the framebuffer size in index.html.
• No persistence. Keep it short enough to play in one sitting. And being randomly generated, scores won't be comparable so don't bother.
• Configurable complexity? ...hard no for js13k. Yes for CD-ROM Edition.
• Continuous or discrete motion? Continuous always feels nicer, but it makes grid-quantized digging a little awkward. ...continuous
• Does anything else in the world behave? Thinking, do we need a concept of sprite controllers, or can we just treat the hero as a one-off kind of thing?
• • Bomb and the unoccupied Boat are sprites.
• • Generalize.

Agenda

• 1. Write the whole game the way I want it, and don't worry about size. Aim to complete by 30 Aug.

• 2. Write the build pipeline: minification, compression, and automated optimization.

• 3. Optimize manually and eliminate features until it fits. That's our js13k release. Aim to complete by 5 Sept.

• 4. Restore all those features and bulk out further, for the Deluxe CD-ROM edition.

• 2026-08-14: Second day, and I'm almost done Phase One. But I want a firmer build pipeline before implementing audio, since there will necessarily be some conversion involved.

• • So, will finish Phase Two before Phase One.

• 2026-08-16: Finished Phase One, and Two was basically done already. Way ahead of schedule!

• 2026-08-16+an hour or so: Phase Three was a breeze, just removing unused graphics got us under the line.

• 2026-08-19: Existing js13k assets have all been upped for cdrom. 749115 bytes. We need to double that at a bare minimum.

• 2026-08-20: Added two more songs and an enormous hello pic, now cdrom edition is over 1.44 MB. Calling it done.

TODO

• js13k submission.
• Deluxe CD-ROM Edition.
• • Copy js13k initially.
• • High resolution graphics.
• • • Bump everything to 96px tiles instead of 16px, and a 1920x1080 framebuffer.
• • • Redraw existing tiles at the higher resolution.
• • • Text: Use CanvasRenderingContext2D's built-in text rendering, no need for our custom 3x5.
• • Rich tiles. Neighbor joining etc.
• • mp3 music instead of synth.
• • Recorded sound effects instead of synth. ...decline. I like the synth sounds.
• • Hello modal.
• • Different kinds of treasure and different ways of detecting them. ...it's too much and i'm losing interest
• Rich cover pic that promises way more than the game can deliver, in the fashion of 80s console games :)
• • js13k wants 320x320 and 800x500 (if it's the same as last year), and itch wants 630x500.
• Mini comic? ...nah

BinarySong ".bs", Song Format For js13k Edition

It's sourced from MIDI and shouldn't look too different from MIDI. But I want a single track, pretty sure we won't need velocity, and we can encode note durations in their On event. No header. Tempo, instruments, channel levels, and all else are hard-coded in the synth. Well actually, tempo is irrelevant. We'll record time in milliseconds, like EAU. Our song has a range of 58 notes, so we can use a 6-bit noteid instead of 7.

The file is a straight stream of events, no header, first byte of the event tells you all about it:

  0ttttttt            Fine Delay. (t+1) ms
  10tttttt            Coarse Delay. ((t+1)*128) ms
  11nnnnnn ccdddddd   Note. (n+0x27) noteid, (c) chid, (d*16) ms. Longest hold is 1008 ms.