diff --git a/backend/Dockerfile b/backend/Dockerfile
index 56023cb..dc8f66f 100644
--- a/backend/Dockerfile
+++ b/backend/Dockerfile
@@ -2,6 +2,10 @@ FROM python:3.13.5-alpine
 
 WORKDIR /app
 
+RUN apk update && apk add git
+
+RUN git clone --depth 1 'https://github.com/yt-dlp/yt-dlp.git' /yt-dlp
+
 COPY requirements.txt ./
 RUN pip install --no-cache-dir -r requirements.txt
 
diff --git a/backend/requirements.txt b/backend/requirements.txt
index 4b83363..7623d9f 100644
--- a/backend/requirements.txt
+++ b/backend/requirements.txt
@@ -1,2 +1,4 @@
 Flask==3.1.0
 flask-cors
+dotenv
+requests
\ No newline at end of file
diff --git a/backend/src/app.py b/backend/src/app.py
index cd551c2..2b636c3 100644
--- a/backend/src/app.py
+++ b/backend/src/app.py
@@ -1,14 +1,48 @@
-from flask import Flask
+import dotenv
+from flask import Flask, Response, jsonify, request
 from flask_cors import CORS
 
+from .room import Room
+from .song import init_db
+
+dotenv.load_dotenv()
+
+
 app = Flask(__name__)
 CORS(app)
 
 
+ROOMS: dict[int, Room] = {}  # { room_id: room, ... }
+
+
+def error(msg: str, status: int = 400) -> Response:
+    res = jsonify({"success": False, "error": msg})
+    res.status_code = status
+    return res
+
+
 @app.route("/api")
 def index():
     return "hello from flask"
 
 
+@app.route("/api/join")
+def join():
+    room_id = request.args.get("room")
+    code = request.args.get("code")
+
+    if room_id is None:
+        return error("Missing room id")
+
+    if (room := ROOMS.get(int(room_id))) is None:
+        return error("Invalid room")
+
+    if room.pin is not None and room.pin != code:
+        return error("Invalid code")
+
+    return {"success": True, "ws": f"/ws/{room_id}"}
+
+
+init_db()
 if __name__ == "__main__":
     app.run(debug=True)
diff --git a/backend/src/connect.py b/backend/src/connect.py
new file mode 100644
index 0000000..962528c
--- /dev/null
+++ b/backend/src/connect.py
@@ -0,0 +1,6 @@
+import sqlite3
+
+
+def get_connection():
+    conn = sqlite3.connect(".data/jukebox.db")
+    return conn
diff --git a/backend/src/room.py b/backend/src/room.py
new file mode 100644
index 0000000..51b96e2
--- /dev/null
+++ b/backend/src/room.py
@@ -0,0 +1,64 @@
+from dataclasses import dataclass
+
+from .song import Song
+
+USER_SCORE_WEIGHT = 0.7
+ARTIST_WEIGHT = 0.1
+TAG_WEIGHT = 0.1
+RANDOM_WEIGHT = 0.1
+RECENT_PENALTY = 0.5
+RECENT_COUNT = 10
+
+
+type UserScoredSong = tuple[Song, int]
+
+
+@dataclass
+class Room:
+    id: int
+    coord: tuple[float, float]
+    name: str
+    pin: int | None
+    tags: set[str]
+
+    songs: dict[str, UserScoredSong]
+    history: list[Song]
+
+    def rank_song(self, song: Song, user_score: int) -> float:
+        rank = 0.0
+        song_items = self.songs.items()
+
+        lowest_score = min(song_items, key=lambda item: item[1][1])[1][1]
+        highest_score = min(song_items, key=lambda item: item[1][1])[1][1]
+
+        rank += translate(user_score, lowest_score, highest_score, 0.0, USER_SCORE_WEIGHT)
+
+        recent_songs = self.history[-RECENT_COUNT:]
+
+        tag_counts = {}
+        artist_counts = {}
+        for song in recent_songs:
+            for tag in song.tags:
+                if tag not in tag_counts:
+                    tag_counts[tag] = 0
+                tag_counts[tag] += 1
+            if song.artist not in artist_counts:
+                artist_counts[song.artist] = 0
+            artist_counts[song.artist] += 1
+
+        tag_total = 0
+        for tag in song.tags:
+            if tag in tag_counts:
+                tag_total += tag_counts[tag]
+
+        rank += translate(tag_total, 0, RECENT_COUNT, 0, TAG_WEIGHT)
+        rank += translate(artist_counts[song.artist], 0, RECENT_COUNT, 0, ARTIST_WEIGHT)
+
+        if song in recent_songs:
+            rank -= RECENT_PENALTY
+
+        return rank
+
+
+def translate(value: float, in_min: float, in_max: float, out_min: float, out_max: float):
+    return (value - in_min) / (in_max - in_min) * (out_max - out_min) + out_min
diff --git a/backend/src/song.py b/backend/src/song.py
new file mode 100644
index 0000000..8570033
--- /dev/null
+++ b/backend/src/song.py
@@ -0,0 +1,29 @@
+from dataclasses import dataclass
+from .connect import get_connection
+
+
+def init_db():
+    conn = get_connection()
+    cursor = conn.cursor()
+    cursor.execute("""
+        CREATE TABLE IF NOT EXISTS songs (
+            mbid TEXT PRIMARY KEY,
+            title TEXT NOT NULL,
+            artist TEXT NOT NULL,
+            tags TEXT NOT NULL,
+            lastfm_image_id TEXT NOT NULL,
+            youtube_id TEXT NOT NULL
+        );
+    """)
+    conn.commit()
+    conn.close()
+
+
+@dataclass
+class Song:
+    mbid: str
+    title: str
+    artist: str
+    tags: list[str]
+    image_id: str
+    youtube_id: str
diff --git a/backend/src/song_fetch.py b/backend/src/song_fetch.py
new file mode 100644
index 0000000..96288e9
--- /dev/null
+++ b/backend/src/song_fetch.py
@@ -0,0 +1,63 @@
+import requests
+import urllib.parse
+import os.path
+import os
+import sys
+
+sys.path.append("/yt-dlp")
+import yt_dlp
+
+
+def lastfm_search(query: str) -> tuple[str, str]:
+    response = requests.get(
+        url="https://ws.audioscrobbler.com/2.0/?method=track.search&format=json",
+        params={"limit": 5, "track": query, "api_key": os.environ["LASTFM_API_KEY"]},
+    )
+
+    assert response.status_code == 200
+
+    track_info = response.json()["results"]["trackmatches"]["track"][0]
+
+    return track_info["name"], track_info["artist"]
+
+
+def lastfm_getinfo(
+    name: str, artist: str
+) -> tuple[str, str, str, str, list[str]]:  # ( id, image_id, tags )
+    response = requests.get(
+        url="https://ws.audioscrobbler.com/2.0/?method=track.getInfo&format=json",
+        params={
+            "track": name,
+            "artist": artist,
+            "api_key": os.environ["LASTFM_API_KEY"],
+        },
+    )
+
+    track_info = response.json()["track"]
+
+    image_url = urllib.parse.urlparse(track_info["album"]["image"][0]["#text"])
+
+    return (
+        track_info["mbid"],
+        [t["name"] for t in track_info["toptags"]["tag"]],
+        os.path.splitext(os.path.basename(image_url.path))[0],
+    )
+
+
+print(yt_dlp, flush=True)
+
+# # def get_yt_mp3link(name: str, artist: str) -> str: ...
+# #     os.popen("/yt-dlp ")
+
+# # /yt-dlp/yt-dlp.sh "ytsearch1:Never gonna give you up" --get-url -f "ba"
+
+# import json
+
+# print(json.dumps(lastfm_getinfo(*lastfm_search("money")), indent=2))
+# exit(1)
+
+
+# # def
+
+
+# ## query ==> lastfm  ==> list of songs ==> take first ==> request song info ==> get YT link ==>  save in DB  ==>
diff --git a/docker-compose.yml b/docker-compose.yml
index ea7e2ca..3b05616 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -1,18 +1,18 @@
 services:
-  backend:
-    build: ./backend
-    ports:
-      - 5001:5000
-    environment:
-        NODE_ENV: development
-    volumes:
-      - ./backend:/app
-      - ./.data/jukebox.sqlite3:/app/.data/jukebox.sqlite3
+    backend:
+        build: ./backend
+        ports:
+            - 5001:5000
+        environment:
+            NODE_ENV: development
+        volumes:
+            - ./backend:/app
+            - ./.data:/app/.data
 
-  frontend:
-    build: ./frontend
-    ports:
-      - 5173:5173
-    volumes:
-      - ./frontend:/app
-      - /app/node_modules
+    frontend:
+        build: ./frontend
+        ports:
+            - 5173:5173
+        volumes:
+            - ./frontend:/app
+            - /app/node_modules
diff --git a/ruff.toml b/ruff.toml
new file mode 100644
index 0000000..d461c74
--- /dev/null
+++ b/ruff.toml
@@ -0,0 +1 @@
+line-length = 200