diff --git a/.dockerignore b/.dockerignore
new file mode 100644
index 0000000..2d03d7c
--- /dev/null
+++ b/.dockerignore
@@ -0,0 +1,12 @@
+# Everything under assets/ whose name starts with _ is the SPRITE PIPELINE, not the game: the
+# generator scripts, the reference poses, and the big source sheets _slice.py cuts the frames out
+# of. That is 34 MB of the 45 MB in assets/, no client ever fetches one, and until now they were
+# all sitting in the image and publicly served. The game loads no underscore-prefixed file — see
+# the SPR list in render.js — so the rule is the prefix, with nothing to maintain per sheet.
+assets/_*
+
+.git
+.env
+HANDOFF.md
+**/__pycache__
+**/.DS_Store