deepgrain-foundry/docs/DESIGN.md

Design

What Deepgrain Foundry is meant to be, how its systems fit together, and the decisions made so far with their reasons. Read the relevant part before changing how the game plays. When the owner decides something new, add it under "Decisions" with the date.

What the owner wants (stated by the owner)

• A Sandustry-style factory and automation game. Every cell is a fine falling-sand grain (one or two screen pixels at normal zoom), not a Terraria-size tile. The world is a Terraria-like side view with dark caves.
• Strictly a factory game. No RPG elements, no enemies, and no character items besides the dig and build tools.
• Real physics, and player-built machines instead of magic converter buildings. Furnaces are built from blocks, metal is cast in molds, and heat, air and gravity do the work. Physics hazards (heat, molten metal) damage builds only.
• Loose material falls; solids hold.
• Copy and paste of builds. Pasting places ghosts that the bot builds from the bag.
• Tool upgrades are earned in a satisfying, not tedious way, not bought with arbitrary credits. So far that means casting them: a drill bit in a Bit mold, a bigger bag in a Tank mold. The owner wants the whole upgrade system redesigned (task t14).
• A hovering bot that flies freely. A limited bag that can be upgraded.
• An economy instead of a rocket or other final goal.
  • Sell materials at the trade dock; refined goods and alloys pay more.
  • Spend the money on buildings.
  • Pay off the $20,000 land claim, then keep growing.
  • A milestone ledger marks progress.
• Machines run without power, for simplicity. The power code (water wheel, shaft, steam engine) is still there but switched off (POWER_FREE in src/sim/pieces.js). Those pieces are hidden from the menu, and old saves keep them.
• Look. Not pixel art. The default is the "smooth look": a smooth, illustrated style with soft, clay-like lighting, drawn by WebGL2. The pixel look stays as an option and is what tests use.
• A water cycle, not springs. Steam rises into clouds and comes back as rain, or as snow where it is freezing.
• Sound. Generated ambient music that changes with depth, and retro chiptune effects.
• No external assets. Everything is drawn and synthesized in code.
• Controls and settings. Modern keyboard and mouse, plus gamepad support, and plenty of graphics and display settings.
• Platform. A web game for now, built and tested by agents locally. A Rust version may come much later, for performance; keeping src/sim/ free of the DOM keeps that open.

The core loop

1. Dig with the resonance drill. Rock shatters into loose grains: rubble, ore, coal, clay, sand.
2. Vacuum up what you want (mark materials in the vacuum menu, F, to take only those), and blow it out where you need it.
3. Build a furnace from wall blocks, with a grate floor over a mold. Charge it with ore and coal, light it, and let the molten metal run into the mold.
4. Bars drop out of the bottom of the mold; collect them and sell them at the trade dock, or fill buyers' orders, which pay more.
5. Better bits (copper, then iron, then steel) open harder rock: granite, then basalt. Deeper ores give tin, zinc, silver and gold, and alloys (bronze, brass) pay more.
6. Automate with belts, screw tubes, filters, fans, pipes and machines. Pay off the claim.

Systems in brief

Details and numbers live in the code and in docs/systems/.

• World:
  • sizes 2048×1024, 3072×1280 or 4096×1536 grains;
  • layers: soil, stone, granite and basalt over a magma sea;
  • ores by depth:
    • coal, copper and clay near the top;
    • tin in the upper stone;
    • iron from about a quarter of the way down;
    • zinc in the middle (stone and granite);
    • silver deep in the granite;
    • gold deepest (granite and basalt);
  • ambient temperature falls with height and rises with depth.
• Materials: 95 material ids, counting air and a few used for built parts. Each is in a phase: solid, powder, liquid, gas, or item (bars).
  • Heat flows between cells. Things melt, freeze, boil, burn and react.
  • Fire needs air: a buried fire chokes, and a fan blowing in makes it hotter.
  • Coal burns at about 1350°C in still air and about 2000°C with a fan.
• Drill: see docs/systems/dig-tools.md. Pulse widths, tuning to one material, hardness by bit tier.
• Building: a 4×4-grain block grid.
  • Blocks: walls of any of several materials, belts, screw tubes, filters, grates, gates, pipes, pumps, outlets.
  • Machines: fan, Refiner, Stone cutter, Silo.
  • Molds: ingot, bit, tank. Ingot bars drop out of the bottom onto whatever is under the mold; leave one open block below and a belt under that carries them off. Ingot molds empty themselves: junk and mixed scrap drop below, slag is thrown away and the grate above is raked. Short stubs stay for the next firing. Removing any mold returns its set metal to the bag: whole bars as bars, the rest as scrap.
  • Build actions: drag for lines, Shift-drag for rectangles, hold G to replace, hold C / X and drag to copy / cut, V to paste, Ctrl+Z to undo, middle mouse to pick, Shift+Q/E to switch build tabs.
• Economy:
  • The trade dock pays for anything dropped through its grate, at the market price.
  • Prices dip when you sell a lot of one thing and recover over minutes.
  • Up to 3 orders at a time pay well over market. Builders' orders want bulk rubble, gravel, sand or stone bricks.
  • You start with $250 and $20,000 of claim debt.
• Weather: steam in the open sky becomes clouds. They drift and rain, or snow when cold. The world's water is counted, so rain only returns what evaporated.
• Waste rock and liquids: see docs/systems/stone-and-liquids.md. It covers the Refiner, pipes, the silo, glass bricks, the stone cutter and builders' orders.

Decisions

The newest are at the bottom. The dates are when the decision was made or built.

Up to 2026-10-19 (early design, stated by the owner): everything in "What the owner wants" above, including:

• the economy replacing a rocket goal;
• machines without power;
• the smooth illustrated look;
• the water cycle instead of springs;
• testing in the pixel look unless graphics are being checked.

2026-10-19 / 20, dig tools. The resonance drill replaced the old drill. See docs/systems/dig-tools.md.

2026-10-22:

• Rock too hard for your bit never crumbles, however small. Crumbling it to ore would give ore without the right bit and confuse players. Crumbling it to stone would lose ore. Instead, world generation makes no tiny hard specks: pieces of 30 grains or fewer become the rock around them, and older saves are cleaned once on load. Iron and zinc veins are fewer and chunkier, with the same total ore.
• Belts and filters next to each other look like one belt. Belt ends are square with rounded corners.
• Dragging belts or filters sets their direction from the drag. R sets it when placing without dragging. An arrow shows the direction while dragging, and the selection card names it.
• Copy and cut are held keys, not a tool. Hold C or X and drag a box; it acts on release. Copy and cut look different. Cut is destructive, but it can be pasted back or undone.
• Ctrl+Z undoes building (up to 80 steps). The bot building ghosts is never a step of its own.
• Holding Ctrl while placing replaces what is built there (moved to G on 2026-10-23).
• Fans melt like copper (1085°C). Put the fan outside the furnace, blowing in through a grate. The game warns when a fan gets close to melting.
• The vacuum takes only marked materials once any are marked, even if the drag starts on something else. The t6 controls below replace the shared ticks; t16 replaces t6's modes.
• The Refiner grinds stone, granite and basalt rubble, gravel, sand and dirt for trace ore, roughly halving the waste. Ore and anything else it cannot grind drop straight through.
• Pipes, pumps and outlets move liquids up to 500°C, one liquid per line. A line is stored as a count, not simulated grains. Water in pipes counts toward the world's water, so the weather does not replace it.

2026-10-23:

• Ingot molds drop bars below automatically. The owner reported bars being thrown into the furnace above and wants belts underneath to carry them off. Blocked bars wait in the trough; short stubs stay for the next firing. The mold cleans itself and rakes the grate after dropping bars or clearing junk.

• Screw tubes carry no more than belts: they move every other tick. For more throughput, build more lines.

• A heap on a belt moves as one, up to 96 grains deep, not just its bottom layer. If a grain is blocked, the load above it stands still and the belt slips underneath; the top no longer slides over a stuck bottom. Filters still let their chosen materials drop through.

• Pick (middle mouse) selects the piece under the cursor with its direction, wall material and filter settings. G no longer picks, as the owner requested (it is now Replace).

• The build menu is a bar of tabs and icon tiles along the bottom: Structure, Moving, Liquids, Machines, Molds. Hover a tile for its full description, cost and placement help; gamepad players see the selected tile’s popup. While building, the top-left card describes the build tool and shows the R/F settings, Replace, ghosts and status.

• No length limit when dragging. Blocks out of the bot's reach become ghosts that it builds when it gets there.

• Pipes are thin: sand, water and anything else loose passes them. Pumps and outlets are solid.

• Uses for waste rock and sand:

  • glass bricks (sand melted with a fan furnace, cast in an Ingot mold);
  • a Silo for storing one loose material, which should look like a real silo, not a magic black hole;
  • builders' orders for bulk rubble, gravel, sand and stone bricks;
  • a Stone cutter that makes stone bricks, which build cut-stone walls.

• Rubble sells for a pittance ($0.02 a grain, gravel $0.03). Dirt still earns nothing.

• Re-refining sand stays allowed. Refiner sand can be refined again, even in stacked refiners until none is left. The owner's reason: it is less profitable than making glass, so players will do it only when they need more ore rather than more money.

• The project moved from a claude.ai artifact to local development with coding agents. It is built from small files, with NOTES.md as the owner's to-do inbox (since 2026-10-24, a kandown board in tasks/).

• Replace is held G, not Ctrl. The owner hit the browser's Ctrl+W (close tab) and Ctrl+D (bookmark) while replacing and flying with WASD, and the game ignored WASD while Ctrl was held.

• The build tool's top-left card describes the build tool, like the other tools' cards: how to place, the build keys, the R/F settings (material, direction, filter), Replace · G and ghosts waiting. The selected piece's name, cost and description are in the menu and its hover popup. The owner asked for a general description rather than the selected building.

• Ingot molds need no F. They push junk and mixed metal out of the bottom as loose grains with the bars, throw slag away and rake the grate. Removing any mold returns its set metal: whole bars as bars, the rest as scrap. The owner asked what F was for once bars dropped on their own, and chose this over keeping F for cleaning.

• Fewer, smaller messages. Molds show only a small percentage, red when blocked or spoiled and gold when a casting waits for F; details are in the hover panel. Bars dropping, blocked molds and set castings no longer pop up cards or toasts. Fan heat is a red marker on the fan; melted tubes and machines get a short red label where they were. Status lines are one short sentence. The owner found the messages too large and too many.

• World sounds are local. Sounds from the world (water sizzling on hot metal or lava, and any other event with a place) are heard around the bot, whatever the zoom: full volume within 24 grains, fading to silent at 96, panned left or right. The owner heard a constant snapping that followed the bot in an older world but not in a new one. It was the sizzle: in the owner's world, water that had found its way down to hot basalt and granite (480-800°C, about 500 grains below the surface) boiled about 48 times a minute, every one at full volume. The first fix faded sounds with distance from the view; zoomed out they were still heard, so the owner asked for a radius around the bot instead.

• The silo has pixel art in the pixel look, drawn grain by grain like the rest of the world; the smooth look keeps the illustrated silo. The owner noticed it looked the same in both.

• Screw tubes use all their lanes. Grains in an up or down tube shift sideways toward the emptier lanes of the block, and grains taken in from the side go to the far lanes first. A block-wide lift fed by a belt from the side now carries about 90% of what the belt brings (before, only the edge lane filled: the owner saw one line on either side). Belts keep their speed.

• Screw tubes carry bars, one whole bar at a time, in line with the grains: a belt pushes a bar into a tube's side, it rides through corners and leaves the mouth. The owner asked how bars should be moved and chose tubes over a separate bar lift.

• Several worlds are kept. Each world has its own save and autosave; the title screen's Worlds list loads, renames and deletes them, and a new or imported world never overwrites another. An old single save becomes 'World 1'. The owner asked for multiple saves.

2026-10-24:

• The to-do list is a kandown board. NOTES.md became one task file per note in tasks/ (Todo for tasks, Backlog for discussions and ideas, Review for "done, please check"). The owner wanted a task tool built for AI agents.
• Wall and mold materials have a menu (F). It lists every wall material with what you have, the cost and the heat it stands; R still cycles. The owner chose F to match the filter menu.
• The camera's drift toward the pointer is a setting ("Camera looks toward the pointer", on by default). The owner doesn't like it.
• Fog of war reveals by line of sight. Unexplored ground is black with a soft edge; the sky and the surface start seen. The owner chose line of sight over a plain circle around the bot.
• Bars pile neatly, and a Bar rack stores them (t1). Bars that come to rest snap to a tidy brick pattern so piles have no air gaps; a Bar rack machine (the Silo for bars) takes them from a belt or tube, counts them and lets them out with F. The owner wanted bar storage that doesn't waste space, like stacked ingots in real life.
• Hopper blocks replace hopper machines (t4). 1-block Grinder and Saw blocks each work what lands on them and drop it below, so a wider row is a wider, faster hopper. The Refiner and Stone cutter leave the build menu; built ones in old saves keep working. The owner wanted hoppers of any width.
• The bag is the vacuum's control panel (t6). Each bag row has separate pick-up and blow marks; a chip on the tool card sets pick-up to everything, only marked, or the same as the first click; R over a grain toggles its pick-up mark. The owner found the shared ticks confusing. As built: T or the chip cycles What I click → Only marked → Everything; adding a mark switches to Only marked and removing the last goes back to What I click. A bag name or Q/E blows one material; ⬆ marks build an even mix (bars are never mixed).
• The vacuum menu replaces the modes (t16, 2026-10-24). Pick-up has no mode: nothing marked takes everything, anything marked takes only those, Shift takes everything for one click. F with the Vacuum (when nothing in reach can be used) or a click on the card opens a menu with ⬇ Pick up and ⬆ Blow toggles per material; the bag rows lose their buttons. T no longer does anything for the vacuum. The owner found t6's version had too many modes.

Ideas not built yet

• Concrete, as a stronger wall material from rubble.
• Upgrade ideas for the drill: an amplifier, a tuning fork, harmonics. Also a Grav pick upgrade tool and mining charges. See docs/systems/dig-tools.md.
• The owner's ideas for later are tasks tagged idea in the Backlog of the task board.