diff --git a/src/common/ecs/README.md b/src/common/ecs/README.md
index 7dc1c759..e461202d 100644
--- a/src/common/ecs/README.md
+++ b/src/common/ecs/README.md
@@ -156,3 +156,31 @@ take up at least one byte if stateful
 might need free list
 need jump table?
 you'd like to change "mode" from any event
+
+need constant folding, set arrays from other exprs
+
+a = [Sprite,-Player]
+foreach a do begin
+  xpos = ypos
+end
+
+    on gowest do with x:[Location]
+---
+    ldy {{<room}}
+    lda {{<Room:west}},y
+    sta {{<room}}
+---
+    on preframe do
+    with y=[SpriteSlot] limit 2
+    with x=y.sprite
+---
+    lda {{<xpos}}
+    {{!SetHorizPos}}
+---
+    on preframe do
+    foreach x=[Missile,HasXpos]
+---
+    lda {{<xpos}}
+    ldy {{<index}}
+    {{!SetHorizPos}}
+---
diff --git a/src/worker/tools/ecs.ts b/src/worker/tools/ecs.ts
index f537cc05..0ca641f1 100644
--- a/src/worker/tools/ecs.ts
+++ b/src/worker/tools/ecs.ts
@@ -2,7 +2,7 @@ import { ECSCompiler } from "../../common/ecs/compiler";
 import { Dialect_CA65, ECSError, EntityManager } from "../../common/ecs/ecs";
 import { CompileError } from "../../common/tokenizer";
 import { CodeListingMap } from "../../common/workertypes";
-import { BuildStep, BuildStepResult, gatherFiles, getWorkFileAsString, putWorkFile, staleFiles } from "../workermain";
+import { BuildStep, BuildStepResult, fixParamsWithDefines, gatherFiles, getWorkFileAsString, putWorkFile, staleFiles } from "../workermain";
 
 export function assembleECS(step: BuildStep): BuildStepResult {
     let em = new EntityManager(new Dialect_CA65()); // TODO
@@ -15,6 +15,7 @@ export function assembleECS(step: BuildStep): BuildStepResult {
     var destpath = step.prefix + '.ca65';
     if (staleFiles(step, [destpath])) {
         let code = getWorkFileAsString(step.path);
+        fixParamsWithDefines(step.path, step.params);
         try {
             compiler.debuginfo = true;
             compiler.parseFile(code, step.path);
@@ -37,7 +38,7 @@ export function assembleECS(step: BuildStep): BuildStepResult {
         nexttool: "ca65",
         path: destpath,
         args: [destpath],
-        files: [destpath, 'vcs-ca65.h'], //TODO
+        files: [destpath].concat(step.files),
         listings
     };
 }
diff --git a/src/worker/workermain.ts b/src/worker/workermain.ts
index 69bddddc..45a6a4fb 100644
--- a/src/worker/workermain.ts
+++ b/src/worker/workermain.ts
@@ -1135,7 +1135,8 @@ var TOOL_PRELOADFS = {
   'fastbasic': '65-atari8',
   'silice': 'Silice',
   'wiz': 'wiz',
-  'ecs': '65-none', // TODO: support multiple platforms
+  'ecs-vcs': '65-none', // TODO: support multiple platforms
+  'ecs-nes': '65-nes', // TODO: support multiple platforms
 }
 
 //const waitFor = delay => new Promise(resolve => setTimeout(resolve, delay)); // for testing