some more cart infrastructure

cart_unpacked.json

@@ -1,6 +1,10 @@
 [
 	{
 		"sheet_type": "code",
-		"value": "return {init: () => {}, update: () => {}, draw: () => {clearScreen(); drawText(0, 0, 'hello world')}}"
+		"value": "x = code_sheet(1);\nreturn {init: () => {y = 0}, update: () => {y += speed; if (y > 127) {y = -6}}, draw: () => {clear_screen(); draw_text(x, y, 'hello world')}}"
+	},
+	{
+		"sheet_type": "code",
+		"value": "speed = 2; return 8"
 	}
 ]