diff --git a/Roadmap.md b/Roadmap.md
index 5b30f44..aadde02 100644
--- a/Roadmap.md
+++ b/Roadmap.md
@@ -17,4 +17,8 @@
 - Write a non-trivial app in EightBall to discover the pain points
 - Optimize virtual machine bytecodes, based on study of real code
   - For example, it would be good to have an instruction to drop n bytes from call stack rather than repeated `POP`, `DROP` as the compiler currently does.
-- High performance VM: hand-coded in 6502 assembly
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+- High performance VM: hand-coded in 6502 assembly
+
+Features will only be added if:
+1. They do not increase the code size so much that it is no longer practical to run EightBall on Apple II and C64.  (VIC20+32K is already a tight fit.)
+2. Language features must have both an interpreter and compiler implementation.
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