# Assets and licence notes

Lean Academy is a **free, non-commercial fan project**. Its Age of Empires II artwork is used under Microsoft's
**Game Content Usage Rules** (https://www.xbox.com/en-US/developers/rules; text fetched 2026-10-27, "Last Updated: January 2015").

> Age of Empires II © Microsoft Corporation. Lean Academy was created under Microsoft's "Game Content Usage Rules" using assets from Age of Empires II, and it is not endorsed by or affiliated with Microsoft.
> Rules: https://www.xbox.com/en-US/developers/rules

The notice is shown in the page footer (`index.html`), in `README.md`, and here. Age of Empires is a trademark of Microsoft.

## How the Rules are respected

* **No reverse engineering.** The game files were never opened or extracted by this project. Every asset below was downloaded from a public community page or repository.
* **Non-commercial.** No ads, no sales, no paywall, no donation button. If it is ever hosted, host it free of charge and on a page that sells nothing.
* **No Microsoft logos** and no Age of Empires title/logo art. The title is "Lean Academy", and the page says it is not endorsed by or affiliated with Microsoft.
* **No game audio** is used.
* Anyone who reuses this project has to follow the same Rules (see the link above). The Rules also grant Microsoft a licence to anything you add to the "game universe" when you distribute an Item.

**Provenance caveat.** The sprites and the grass come from images hosted on the Age of Empires Fandom wiki, which tags them as fair use and does not say how the uploaders produced them.
The Rules forbid *you* from reverse-engineering the game to get assets; they do not speak to third-party rips. If that matters, swap those four sprite sets for your own in-game screenshots (the Rules allow screenshots).

## Real Age of Empires II assets (files in `public/aoe2/`)

### Unit icons, tech icons, age icons, resource icons, paper texture
Source repository: https://github.com/SiegeEngineers/aoe2techtree (code MIT, © 2018 HSZemi; `img/README` says: "Game Icons © Hidden Path Entertainment, Forgotten Empires, SkyBox Labs, Ensemble Studios").
Picture indices come from `https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/data/trees/BRITONS.json`.

| File | Used for | Source URL |
|---|---|---|
| `ui/Unit_17.png` | Archer icon | https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/img/Unit/17.png |
| `ui/Unit_18.png` | Crossbowman icon | https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/img/Unit/18.png |
| `ui/Unit_20.png` | Skirmisher icon | https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/img/Unit/20.png |
| `ui/Unit_21.png` | Elite Skirmisher icon (also the favicon) | https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/img/Unit/21.png |
| `ui/Tech_34.png` | Fletching | https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/img/Tech/34.png |
| `ui/Tech_35.png` | Bodkin Arrow | https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/img/Tech/35.png |
| `ui/Tech_37.png` | Bracer | https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/img/Tech/37.png |
| `ui/Tech_49.png` | Padded Archer Armor | https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/img/Tech/49.png |
| `ui/Tech_50.png` | Leather Archer Armor | https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/img/Tech/50.png |
| `ui/Tech_51.png` | Ring Archer Armor | https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/img/Tech/51.png |
| `ui/Building_0.png` | Archery Range (section heading) | https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/img/Building/0.png |
| `ui/Building_4.png` | Blacksmith (section heading) | https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/img/Building/4.png |
| `ui/Ages_base_feudal_age.png` | Feudal Age badge | https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/img/Ages/base_feudal_age.png |
| `ui/Ages_base_castle_age.png` | Castle Age badge | https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/img/Ages/base_castle_age.png |
| `ui/food.png`, `wood.png`, `gold.png`, `stone.png` | Resource bar | https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/img/{food,wood,gold,stone}.png |
| `ui/bg_paper.jpg` | Paper texture behind sections | https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/img/Backgrounds/bg_aoe2_hd_paper.jpg |

Unit costs shown in the resource bar (Archer 25 wood 45 gold, Crossbowman 25 wood 45 gold, Skirmisher / Elite Skirmisher 35 wood 25 food) come from
https://github.com/SiegeEngineers/aoe2techtree/blob/master/data/data.json (`data.Unit`), the same file the model's stats come from.

### Unit sprites (in-game Definitive Edition poses, with alpha)
Hosted on the Age of Empires Wiki (Fandom), https://ageofempires.fandom.com, both tagged `Fairuse`. Cut apart with a script: the three units of each image were cropped individually, the soft drop shadow was split off as its own layer, and a red team colour was made by recolouring the blue player-colour pixels.

| Files | Unit | Source image | File page |
|---|---|---|---|
| `sprites/archer_*.png` | Archer (left of the image) | https://static.wikia.nocookie.net/ageofempires/images/5/52/Archerline.png/revision/latest?cb=20200511191144 | https://ageofempires.fandom.com/wiki/File:Archerline.png |
| `sprites/xbow_*.png` | Crossbowman (middle; the wiki caption says so) | same image | same page |
| `sprites/skirm_*.png` | Skirmisher (left; the wiki caption says so) | https://static.wikia.nocookie.net/ageofempires/images/c/c2/Skirmisherline_aoe2de.png/revision/latest?cb=20251220084338 | https://ageofempires.fandom.com/wiki/File:Skirmisherline_aoe2de.png |
| `sprites/eskirm_*.png` | Elite Skirmisher (middle of the line; **inferred from order**: the wiki doesn't caption it, and the image's third unit looks like the Imperial upgrade) | same image | same page |

`*_shadow.png` is the shadow layer of the same sprite. Blue = the original player colour, red = recoloured by code.

### Lean Academy additions (guide character and age icons)
| Files | Used for | Source |
|---|---|---|
| `ui/Unit_33.png` (Monk icon), `ui/Unit_15.png` (Villager icon, currently unused) | Lesson icon, nav, favicon of `learn.html` | https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/img/Unit/33.png and `/15.png` (same repository and terms as the other icons above) |
| `ui/Ages_base_dark_age.png`, `ui/Ages_base_imperial_age.png` | Age progress bar (with the Feudal and Castle badges above) | https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/img/Ages/base_dark_age.png and `base_imperial_age.png` |
| `ui/Building_7.png` (Castle), `ui/Building_10.png` (Monastery), `ui/Building_28.png` (Town Center) | Lesson icons | https://raw.githubusercontent.com/SiegeEngineers/aoe2techtree/master/img/Building/{7,10,28}.png |
| `sprites/monk_front.png` ("Brother Lemma", the guide), `sprites/monk_relic.png` (celebration toast) | The tutorial's guide character | Age of Empires Wiki (Fandom), both files tagged as scenario-editor images: https://static.wikia.nocookie.net/ageofempires/images/5/52/Catholic_Monks_2DE.png/revision/latest?cb=20250526093918 (File page https://ageofempires.fandom.com/wiki/File:Catholic_Monks_2DE.png) and https://static.wikia.nocookie.net/ageofempires/images/c/c5/Catholic_Monks_with_Relic_2DE.png/revision/latest?cb=20250526095042 (File page https://ageofempires.fandom.com/wiki/File:Catholic_Monks_with_Relic_2DE.png). One of the eight monks in each image was cut out by colour-keying the grass. The same provenance caveat as the other sprites applies. |

### Grass terrain
`grass_tile.jpg`: a clean 300x300 patch of in-game grass cut out of a Definitive Edition screenshot, high-passed and cross-faded so it tiles.
Source: https://static.wikia.nocookie.net/ageofempires/images/f/f7/Ao2de_skirmisher_sprites.png/revision/latest?cb=20220830161153
(File page: https://ageofempires.fandom.com/wiki/File:Ao2de_skirmisher_sprites.png, tagged `Fairuse`).

## What is NOT real game art (drawn in code, `src/battlefield.js` and `src/style.css`)

* **Animation.** Only one pose per unit exists. "Attack" is a 2 px recoil and a hop, "death" is the sprite toppling over and darkening. There are no real walk, attack or death frames. The units never move.
* **Arrows and javelins**, their ground shadows, damage numbers, health bars and the team-coloured selection rings.
* **HUD frame.** The top resource bar, bottom command panel, minimap diamond, stone/gold bevels and the end-of-battle banner. They imitate the look of the in-game interface; none of the game's UI textures were used.
* **Isometric feel.** The 2:1 tile grid, the dirt patch and the diamond formation lattice.
* **Trees, buildings, villagers** are not shown at all. (The Lean Academy shows one real monk sprite as its guide; its speech bubbles, XP bar and goal-state panels are drawn in code.)
* **Fonts** are not the game's. Cinzel (a Trajan-style capital face), EB Garamond and JetBrains Mono are bundled under the SIL Open Font License (`public/fonts/LICENSES.txt`).

## Not used
The game's audio, logos and title art, and the civilization emblems.