Ember Forge

An alchemical smelting idle/incremental game written in Common Lisp using SDL2.

You start with a crumbling furnace and a pile of raw stone. Mine ore, discover alloys, unlock ancient recipes, and build a sprawling forge-town that runs itself. The core loop is:

mine → smelt → combine → automate → prestige

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Features

• 7 resource tiers — from humble Stone up to rare Ember Crystals, plus intermediate crafted goods (Steel Plate, Rivets, Machine Parts)
• Smelting queue — up to 5 (expandable via upgrades) concurrent smelt jobs with real-time progress bars
• Building system — purchase and stack buildings that auto-produce resources every tick
• Upgrade tree — unlock new recipes, boost production multipliers, expand storage, and expand your operation
• Shop — buy persistent per-run bonuses using Coins (discount stacking, sell boosts, storage expansion, and more)
• Prestige / Ascension — reset for Ember Essence and buy permanent Eternal Upgrades that carry over every run
• Random events — cave-ins, wandering merchants, and ember pulses keep runs fresh
• Offline progress — up to 8 hours of production is applied when you reload your save
• Achievements — cosmetic milestones tracked across your session
• Human-readable save file — stored as a plain Lisp plist at ~/.local/share/ember-forge/save.lisp

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Requirements

Linux

Dependency	Notes
SBCL	Common Lisp compiler
SDL2	Windowing & rendering
SDL2_ttf	Font rendering
SDL2_image	Image loading
Quicklisp	With sdl2, sdl2-ttf, sdl2-image, alexandria

Windows

Dependency	Notes
SBCL for Windows	sbcl.org
Quicklisp	quicklisp.org
SDL2 runtime DLLs	SDL2.dll, SDL2_image.dll, SDL2_ttf.dll + dependencies
libffi-8.dll	Required by CFFI

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Running & Building

Run from source (Linux / macOS)

./run.sh

Build a Linux binary

./build.sh
./dist/ember-forge

Build a Windows binary (on Windows)

build.bat
dist\ember-forge.exe

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Gameplay Overview

Resources & Tiers

Tier	Resources	Unlocked by
0	Stone, Coal, Coins	Start
1	Iron Ore, Copper Ore, Tin Ore	50+ stone
2	Iron Bar, Copper Bar	Own any mine
3	Bronze Bar, Gear, Bellows, Rivets	10 iron bars / Metalworking upgrade
4	Steel Bar, Steel Plate	Steel Alloy upgrade / Metalworking upgrade
5	Machine Part, Mythril Ore	Industrial Tools upgrade / Deep Drilling upgrade
6	Ember Crystal	1+ Mythril Drill
∞	(prestige loop)	First Ember Crystal

Buildings

Buildings are purchased with resources and produce goods automatically every game tick. Costs scale by ×1.15 per building owned. Notable buildings:

• Rusty Pickaxe — mines Stone passively (0.5/s)
• Coal Pit — produces Coal (0.3/s)
• Iron Mine — extracts Iron Ore (0.2/s); unlocks at 50 Stone ever mined
• Copper Mine — extracts Copper Ore (0.2/s); unlocks at 50 Stone ever mined
• Tinsmith — refines Tin Ore for alloying (0.15/s)
• Market Stall — generates Coins passively (0.35/s); unlocks at 100 Stone ever mined
• Auto-Furnace — automatically runs iron-bar smelt jobs; adds one smelting slot
• Bellows Workshop — speeds up all active smelting by 10% per workshop owned
• Mythril Drill — unlocked by the Deep-Core Drilling upgrade; mines Mythril (0.05/s)

Smelting

Open the Forge panel and queue up to 5 recipes simultaneously. Each job consumes input resources on enqueue and deposits outputs when complete. Slot count is expandable via the Second and Third Crucible upgrades.

Recipe	Inputs	Output	Time	Unlock
Smelt Iron Bar	3 Iron Ore + 1 Coal	1 Iron Bar	4 s	Always
Smelt Copper Bar	3 Copper Ore + 1 Coal	1 Copper Bar	4 s	Always
Cast Gear	1 Iron Bar	1 Gear	3 s	Always
Alloy Bronze	2 Copper Bar + 1 Tin Ore	1 Bronze Bar	8 s	Own any Copper Bar + Tin Ore
Craft Bellows	2 Bronze Bar + 2 Coal	1 Bellows	10 s	Always
Forge Rivets	1 Iron Bar + 1 Coal	8 Rivets	6 s	Metalworking upgrade
Forge Steel	2 Iron Bar + 3 Coal	1 Steel Bar	12 s	Steel Alloy Research upgrade
Machine Gears	1 Steel Bar	3 Gears	6 s	1+ Steel Bar ever
Hammer Steel Plate	2 Steel Bar + 1 Coal	1 Steel Plate	14 s	Metalworking upgrade
Mint Trade Tokens	1 Bronze Bar + 1 Gear	250 Coins	10 s	Coin Minting upgrade
Assemble Machine Part	2 Gear + 1 Steel Plate + 10 Rivets	1 Machine Part	22 s	Industrial Tools upgrade
Condense Ember Crystal	10 Mythril Ore + 5 Steel Bar	1 Ember Crystal	30 s	Own 1+ Mythril Drill

Upgrade Tree

Upgrades are purchased once with resources. A selection of notable upgrades:

Upgrade	Effect
Sturdy Gloves	Double click mining power
Miner's Pouch	Double manual gathering yield
Quick Hands	Manual actions 0.5 s faster
Hardened Pickaxes	Pickaxes mine 2× faster
Gear-Driven Picks	Pickaxes mine 75% faster
Deep Coal Seams	Coal Pits produce 50% more coal
Furnace Tuning	All smelting 25% faster
Second Crucible	+1 smelting slot
Third Crucible	+1 smelting slot
Market Network	Market Stalls generate 2× coins
Bright Signage	Market Stalls generate +50% coins
Reinforced Sacks	Stone/Coal storage +50%
Ore Crates	Ore storage +50%
Precision Molds	Gears, Bellows, and Rivets craft 2× output
Steel Alloy Research	Unlocks steel smelting recipe
Metalworking	Unlocks Steel Plates and Rivets recipes
Coin Minting	Unlocks the Trade Token minting recipe
Ancient Veins	+50% ore production from all mines
Deep-Core Drilling	Unlocks Mythril Drill building
Industrial Tools	Unlocks Machine Parts; Mythril Drills +50%

Shop

The Shop panel lets you spend Coins on stackable per-run bonuses. Effects apply immediately and persist until you Ascend.

Item	Max Level	Effect per level
Haggling Lessons	10	Shop prices −5% (floor: 60% of base)
Salesmanship	12	Sell values +10% (cap: 3×)
Warehouse Lease	8	All storage caps +15%
Smelter's Coupon	10	Smelting speed +10%
Foreman Contract	10	All building production +7%

Shop costs scale by a per-item factor each level (1.6×–2.0×). Buying resources directly from the shop is also available for any resource that has a sell value — prices are calibrated to prevent buy-then-sell arbitrage.

Prestige (Ascension)

Once you produce your first Ember Crystal, the Ascend button lights up. Ascending resets resources, buildings, and upgrades in exchange for Ember Essence:

Essence earned = floor(sqrt(total_ember_ever_produced)) + (ascensions × 2)

Essence is spent in the Prestige panel on Eternal Upgrades that persist across all future runs:

Upgrade	Cost	Effect
Eternal Miner	5	Start each run with 1 free Pickaxe
Ember Memory	10	Keep 10% of coins on reset
Forge Mastery	25	All smelting permanently 25% faster
Ancient Veins	50	+50% all ore production permanently
Twin Furnaces	100	Start with Auto-Furnace already built

Random Events

Events fire roughly every 5–15 minutes and present a modal choice:

• Cave-In — spend stone to repair or lose iron production temporarily
• Wandering Merchant — trade refined bars for rarer materials
• Ember Pulse — double smelt speed for 30 seconds

Keyboard Shortcuts

Key	Action
1	Forge panel
2	Mine panel
3	Upgrades panel
4	Recipes panel
5	Shop panel
6	Prestige panel
Esc	Main menu
F11	Toggle fullscreen

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Project Structure

ember-forge/
├── ember-forge.asd              # ASDF system definition
├── src/
│   ├── package.lisp             # Package definition
│   ├── dsl.lisp                 # Macro DSL for game content tables
│   ├── main.lisp                # Entry point, game loop (60 fps)
│   ├── state.lisp               # Global game-state struct
│   ├── resources.lisp           # Resource definitions & registry
│   ├── recipes.lisp             # Recipe definitions & smelt queue logic
│   ├── buildings.lisp           # Building definitions & tick logic
│   ├── upgrades.lisp            # Upgrade tree definitions
│   ├── shop.lisp                # Shop items, buy/sell logic, economy modifiers
│   ├── events.lisp              # Random event system
│   ├── prestige.lisp            # Prestige / ascension logic
│   ├── ui/
│   │   ├── renderer.lisp        # Master render dispatcher
│   │   ├── panel-forge.lisp     # Forge panel (click-to-mine + smelt queue)
│   │   ├── panel-mine.lisp      # Mine / resource overview panel
│   │   ├── panel-upgrades.lisp  # Upgrade tree panel
│   │   ├── panel-recipes.lisp   # Recipe browser panel
│   │   ├── panel-shop.lisp      # Building shop panel
│   │   ├── panel-prestige.lisp  # Prestige & eternal upgrades panel
│   │   ├── menu.lisp            # Main menu
│   │   ├── widgets.lisp         # Button, label, progress-bar primitives
│   │   ├── tooltip.lisp         # Hover tooltip system
│   │   ├── notifs.lisp          # Floating toast notifications
│   │   ├── backgrounds.lisp     # Background image rendering
│   │   └── theme.lisp           # Color palette & font handles
│   └── util/
│       ├── math.lisp            # lerp, clamp, large-number formatting
│       ├── timer.lisp           # Delta-time tracking
│       ├── fonts.lisp           # Font loading helpers
│       ├── options.lisp         # User options / settings
│       └── save.lisp            # Serialise / deserialise state to file
├── assets/
│   ├── backgrounds/             # Panel background images (PNG)
│   └── fonts/                   # Bundled TTF/OTF fonts
├── scripts/
│   └── build-release.lisp       # Release build script
├── build.sh                     # Linux build script
├── build.bat                    # Windows build script
├── run.sh                       # Run from source (Linux)
└── logo.png

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Content DSL (Macros)

Most game content is defined declaratively via macros in src/dsl.lisp (and used in the src/* definition files). This keeps the “data tables” readable while still producing the same runtime structs/hash-tables.

Macros

• defresources → *resource-defs* + *sell-values*
• defbuildings → *buildings*
• defrecipes → *recipes*
• defupgrades → *upgrades*
• defshop-items → *shop-items*
• defeternal-upgrades → *eternal-upgrades*
• defevents + (choice ...) → *events*
• defachievements → *achievements*

Conventions

• :unlock / :effect / :apply are written as plain expressions; the DSL wraps them into lambdas.
  • State is s (and shop :apply also receives lvl).
• Plists like costs/inputs/outputs/production are written unquoted (the DSL quotes them).

Example:

(defbuildings
  (:iron-mine "Iron Mine" "Extracts iron ore from deep veins."
   :cost (:coins 200.0d0 :stone 100.0d0)
   :produces (:iron 0.2d0)
   :unlock (>= (resource-ever s :stone) 50.0d0)))

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Technical Notes

• Language: Common Lisp (SBCL recommended)
• Rendering: SDL2 primitives + TTF fonts — no external sprite sheets besides some basic background images
• Window size: 1280 × 768
• Target frame rate: 60 fps (16 ms tick)
• All production math uses double-float to avoid integer overflow at high prestige counts
• Delta-time is capped at 0.5 s to prevent large jumps after alt-tab
• Autosave every 60 seconds of real time to ~/.local/share/ember-forge/save.lisp
• Multiple save slots supported (save-slot field in game state)
• Offline production computed on load (capped at 8 hours)

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License

See individual font subdirectories under assets/fonts/ for third-party font licenses.