diff --git a/Pipfile b/Pipfile
new file mode 100644
index 0000000..b5846df
--- /dev/null
+++ b/Pipfile
@@ -0,0 +1,11 @@
+[[source]]
+name = "pypi"
+url = "https://pypi.org/simple"
+verify_ssl = true
+
+[dev-packages]
+
+[packages]
+
+[requires]
+python_version = "3.8"
diff --git a/Pipfile.lock b/Pipfile.lock
new file mode 100644
index 0000000..e42812c
--- /dev/null
+++ b/Pipfile.lock
@@ -0,0 +1,20 @@
+{
+    "_meta": {
+        "hash": {
+            "sha256": "7f7606f08e0544d8d012ef4d097dabdd6df6843a28793eb6551245d4b2db4242"
+        },
+        "pipfile-spec": 6,
+        "requires": {
+            "python_version": "3.8"
+        },
+        "sources": [
+            {
+                "name": "pypi",
+                "url": "https://pypi.org/simple",
+                "verify_ssl": true
+            }
+        ]
+    },
+    "default": {},
+    "develop": {}
+}
diff --git a/app/__init__.py b/app/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/app/config.py b/app/config.py
new file mode 100644
index 0000000..ffe2d00
--- /dev/null
+++ b/app/config.py
@@ -0,0 +1,2 @@
+# 16 quadrillion
+MAX_NUM = 16_000_000_000_000_000
diff --git a/math_game.py b/app/math_game.py
similarity index 60%
rename from math_game.py
rename to app/math_game.py
index dbf9940..4219e8b 100644
--- a/math_game.py
+++ b/app/math_game.py
@@ -1,12 +1,24 @@
 # copyright 2020 Simon Averbach and Zev Averbach
+from config import MAX_NUM
+
 
 def math_game():
+    for i in range(100):
+        print()
     print("Hi, welcome to math game!")
     print("How high do you want to count?")
     number = int(input("> "))
+    while number > MAX_NUM:
+        print(f"Sorry, there's a limit of {MAX_NUM:,}")
+        print("How high do you want to count?")
+        number = int(input("> "))
     print("How much do you want to add each time?")
     each = int(input("> "))
     print(f"Okay, here we go! We're going to count from zero to {number} by {each} at a time.")
     sleep(3)
     for i in range(0, number, each):
         print(f"{i:,}")
+
+
+if __name__ == "__main__":
+    math_game()