diff --git a/api.py b/api.py
new file mode 100644
index 0000000..901647e
--- /dev/null
+++ b/api.py
@@ -0,0 +1,142 @@
+from fastapi import FastAPI, HTTPException
+from pydantic import BaseModel
+import sqlite3
+import time
+
+DB_FILE = "cosmic_timer.db"
+
+app = FastAPI()
+
+def get_db_conn():
+    conn = sqlite3.connect(DB_FILE)
+    conn.row_factory = sqlite3.Row
+    return conn
+
+class UserModel(BaseModel):
+    username: str
+
+@app.post("/session/start")
+def start_session(user: UserModel):
+    username = user.username.strip() or "Anonymous"
+    conn = get_db_conn()
+    c = conn.cursor()
+
+    # Ensure user exists
+    c.execute("SELECT 1 FROM users WHERE username = ?", (username,))
+    if not c.fetchone():
+        c.execute("INSERT INTO users (username) VALUES (?)", (username,))
+
+    # Insert session start
+    c.execute("INSERT INTO sessions (username) VALUES (?)", (username,))
+    session_id = c.lastrowid
+
+    conn.commit()
+    conn.close()
+    return {"session_id": session_id, "username": username, "message": f"Session started for {username}"}
+
+@app.post("/session/{session_id}/stop")
+def stop_session(session_id: int):
+    conn = get_db_conn()
+    c = conn.cursor()
+
+    c.execute("SELECT start_time, username FROM sessions WHERE session_id = ?", (session_id,))
+    row = c.fetchone()
+    if not row:
+        conn.close()
+        raise HTTPException(status_code=404, detail="Session not found")
+
+    # Calculate duration
+    start_time_str = row["start_time"]
+    username = row["username"]
+
+    try:
+        start_time = time.mktime(time.strptime(start_time_str, "%Y-%m-%d %H:%M:%S"))
+    except Exception:
+        conn.close()
+        raise HTTPException(status_code=500, detail="Invalid start_time format in DB")
+
+    end_time = time.time()
+    duration_seconds = int(end_time - start_time)
+
+    # Update session end time and duration
+    c.execute("UPDATE sessions SET end_time = CURRENT_TIMESTAMP, duration_seconds = ? WHERE session_id = ?", (duration_seconds, session_id))
+
+    # Update user lifetime_seconds (add duration)
+    c.execute("SELECT lifetime_seconds FROM users WHERE username = ?", (username,))
+    current_lifetime = c.fetchone()[0] or 0
+    new_lifetime = current_lifetime + duration_seconds
+
+    # Recalculate carbon footprint and entropy score (simplified here)
+    CARBON_PER_SECOND_KG = 0.0000005
+    carbon_footprint = new_lifetime * CARBON_PER_SECOND_KG
+
+    # Get trivia event count for entropy calculation
+    c.execute("SELECT COUNT(*) FROM trivia_events WHERE username = ?", (username,))
+    trivia_events_count = c.fetchone()[0] or 0
+
+    def calculate_entropy_score(trivia_events_count, total_seconds):
+        import math
+        if total_seconds == 0 or trivia_events_count == 0:
+            return 0.0
+        p = trivia_events_count / total_seconds
+        entropy = -p * math.log2(p) - (1 - p) * math.log2(1 - p) if 0 < p < 1 else 0
+        return entropy * total_seconds
+
+    entropy_score = calculate_entropy_score(trivia_events_count, new_lifetime)
+
+    c.execute('''
+        UPDATE users SET lifetime_seconds = ?, carbon_footprint_kg = ?, entropy_score = ? WHERE username = ?
+    ''', (new_lifetime, carbon_footprint, entropy_score, username))
+
+    conn.commit()
+    conn.close()
+
+    return {
+        "session_id": session_id,
+        "username": username,
+        "duration_seconds": duration_seconds,
+        "carbon_footprint_kg": carbon_footprint,
+        "entropy_score": entropy_score,
+        "message": f"Session stopped and stats updated for {username}"
+    }
+
+@app.get("/leaderboard")
+def get_leaderboard():
+    conn = get_db_conn()
+    c = conn.cursor()
+
+    # Top 10 users by lifetime_seconds
+    c.execute("SELECT username, lifetime_seconds FROM users ORDER BY lifetime_seconds DESC LIMIT 10")
+    lifetime_lb = [{"username": r["username"], "lifetime_seconds": r["lifetime_seconds"]} for r in c.fetchall()]
+
+    # Top 10 users by trivia_points
+    c.execute("SELECT username, trivia_points FROM users ORDER BY trivia_points DESC LIMIT 10")
+    trivia_lb = [{"username": r["username"], "trivia_points": r["trivia_points"]} for r in c.fetchall()]
+
+    conn.close()
+    return {
+        "top_lifetime_users": lifetime_lb,
+        "top_trivia_users": trivia_lb,
+    }
+
+@app.get("/user/{username}/stats")
+def get_user_stats(username: str):
+    conn = get_db_conn()
+    c = conn.cursor()
+
+    c.execute("SELECT * FROM users WHERE username = ?", (username,))
+    row = c.fetchone()
+    if not row:
+        conn.close()
+        raise HTTPException(status_code=404, detail="User not found")
+
+    stats = {
+        "username": row["username"],
+        "lifetime_seconds": row["lifetime_seconds"],
+        "trivia_points": row["trivia_points"],
+        "carbon_footprint_kg": row["carbon_footprint_kg"],
+        "entropy_score": row["entropy_score"],
+    }
+    conn.close()
+    return stats
+
diff --git a/cosmic_runtime.json b/cosmic_runtime.json
new file mode 100644
index 0000000..f3a20fd
--- /dev/null
+++ b/cosmic_runtime.json
@@ -0,0 +1 @@
+{"total_runtime": 3398}
\ No newline at end of file