Simple chessboard design + slove button (shows you the solution with the algorithm) and marks conflicts with damen red.

conflict still has some errors (damen despawn somethimes) and css is very simple.

app/routes/main_routes.py

@@ -1,4 +1,4 @@
-from flask import Blueprint, render_template
+from flask import Blueprint, jsonify, render_template, request
 from flask_login  import login_required, current_user
 
 main_bp = Blueprint("main", __name__)
@@ -11,3 +11,54 @@ def home():
 @login_required
 def dashboard():
     return render_template('dashboard.html', user=current_user)
+
+@main_bp.route("/check", methods=["POST"])
+def check():
+    data = request.json
+    board = data["board"]
+    row = data["row"]
+    col = data["col"]
+
+    for r in range(len(board)):
+        c = board[r]
+
+        if c == -1 or r == row:
+            continue
+
+        # gleiche Spalte
+        if c == col:
+            return jsonify({"valid": False})
+
+        # gleiche Diagonale
+        if abs(c - col) == abs(r - row):
+            return jsonify({"valid": False})
+
+    return jsonify({"valid": True})
+
+
+@main_bp.route("/solve")
+def solve():
+    n = 8
+    solutions = []
+    board = [-1] * n
+
+    def is_safe(row, col):
+        for r in range(row):
+            c = board[r]
+            if c == col or abs(c - col) == abs(r - row):
+                return False
+        return True
+
+    def backtrack(row):
+        if row == n:
+            solutions.append(board[:])
+            return
+
+        for col in range(n):
+            if is_safe(row, col):
+                board[row] = col
+                backtrack(row + 1)
+                board[row] = -1
+
+    backtrack(0)
+    return jsonify(solutions)