diff --git a/src/a23d2.c b/src/a23d2.c
index d44954e..7ec501b 100644
--- a/src/a23d2.c
+++ b/src/a23d2.c
@@ -26,7 +26,7 @@
 #include <string.h>  // For memcopy
 
 
-volatile cameraT   *_camera = (cameraT *)0x200; // Simulation copy of camera.
+volatile cameraT   *_camera = (cameraT *)CAMERA_SHARED_START; // Simulation copy of camera.
 volatile cameraT   *_cameraInDatabase;
 volatile byte      *_pointer;
 
@@ -132,7 +132,7 @@ void a23d2Init(void) {
 	POKE(MMU_MEM_BANK_3, A23D2_FAR_BLOCK);
 
 	// We're going to clobber from 0x80fb to 0x8101.  Back it up.
-	memcpy((byte *)(0x2ff - 0x06), (byte *)A23D2_TEST_DATABASE, 0x06);
+	scdMemCpy((byte *)(SCRATCH_END - 0x06), (byte *)A23D2_TEST_DATABASE, 0x06);
 
 	// Initialize A2-3D2 so we can use the "fast entry point" (NXTPT) when rendering.
 	_bytes   = 0;
@@ -144,11 +144,21 @@ void a23d2Init(void) {
 	_pointer[_bytes++] = 0;
 	_pointer[_bytes++] = END;    // Setup complete!
 
-//	__attribute__((leaf)) asm volatile("jsr %[addy]":: [addy] "i"(A23D2_ENTRYS));  // Call ENTRYS.  This preserves the ZP for us.
-	__attribute__((leaf)) asm volatile("jsr 0x606c");  // Call ENTRYS.  This preserves the ZP for us.
+	// Save ZP that A2-3D2 is going to clobber.
+	scdMemCpy((byte *)(SCRATCH_END - COMPILER_ZP_LENGTH), (byte *)COMPILER_ZP_START, COMPILER_ZP_LENGTH);
+
+	// Call ENTRYN.  This sets up A2-3D2.  We need to preserve processor state and ZP.
+	__attribute__((leaf)) asm volatile("jsr %[addy]":: [addy] "i"(A23D2_ENTRYN));
+
+	// Save A2-3D2s variables for later.
+	scdMemCpy((byte *)VARS_1_START, (byte *)A23D2_VARS_1_START, A23D2_VARS_1_LENGTH);
+	scdMemCpy((byte *)VARS_2_START, (byte *)A23D2_VARS_2_START, A23D2_VARS_2_LENGTH);
+
+	// Restore ZP that A2-3D2 clobbered.
+	scdMemCpy((byte *)COMPILER_ZP_START, (byte *)(SCRATCH_END - COMPILER_ZP_LENGTH), COMPILER_ZP_LENGTH);
 
 	// Put back the RAM we clobbered.
-	memcpy((byte *)A23D2_TEST_DATABASE, (byte *)(0x2ff - 0x06), 0x06);
+	scdMemCpy((byte *)A23D2_TEST_DATABASE, (byte *)(SCRATCH_END - 0x06), 0x06);
 
 	// Move our 3D/2D data buffer at 0x56000 into slot 4.
 	POKE(MMU_MEM_BANK_4, DATABASE_FAR_BLOCK);
@@ -174,8 +184,6 @@ void a23d2Init(void) {
 
 
 void a23d2Render(void) {
-	uint16_t i;
-
 	// We need to manually page 0x54000 into 0x6000.
 	// This isn't actually large enough for A2-3D2 but what we should only
 	// lose Apple ][ stuff we're not using anyway.
@@ -195,30 +203,25 @@ void a23d2Render(void) {
 	_cameraInDatabase->b = _camera->b;
 	_cameraInDatabase->h = _camera->h;
 
-	//memcpy((byte *)(0x2ff - A23D2_ZP_LENGTH), (byte *)A23D2_ZP_START, A23D2_ZP_LENGTH);  // Save the ZP we're going to clobber.
+	// Save ZP that A2-3D2 is going to clobber.
+	scdMemCpy((byte *)(SCRATCH_END - COMPILER_ZP_LENGTH), (byte *)COMPILER_ZP_START, COMPILER_ZP_LENGTH);
 
-	for (i=0; i<A23D2_ZP_LENGTH; i++) POKE(0x2ff + i, PEEK(A23D2_ZP_START + i));
+	// Restore A2-3D2s variables.
+	scdMemCpy((byte *)A23D2_VARS_1_START, (byte *)VARS_1_START, A23D2_VARS_1_LENGTH);
+	scdMemCpy((byte *)A23D2_VARS_2_START, (byte *)VARS_2_START, A23D2_VARS_2_LENGTH);
 
-/*
-	__attribute__((leaf)) asm volatile( \
-		"     ldx #%[length]  \n" \
-		"%=:                  \n" \
-		"     lda %[start],x  \n" \
-		"     sta %[dest],x   \n" \
-		"     dex             \n" \
-		"     bne %=b         \n" \
-		:  \
-		: [length] "i"(A23D2_ZP_LENGTH), [start] "i"(A23D2_ZP_START), [dest] "i"(0x2ff) \
-		: "a", "x", "c", "v");
-*/
+	// Set IBP.
+	POKEW(A23D2_IBP, DATABASE);
 
-	POKEW(A23D2_IBP, DATABASE);  // Set IBP.
-//	__attribute__((leaf)) asm volatile("jsr %[addy]":: [addy] "i"(A23D2_NXTPT) : "a","x","y","c","v");    // Call NXTPT.
-	__attribute__((leaf)) asm volatile("jsr 0x6118"::: "a","x","y","c","v");    // Call NXTPT.
+	// Call NXTPT.
+	__attribute__((leaf)) asm volatile("jsr %[addy]":: [addy] "i"(A23D2_NXTPT) : "a","x","y","c","v");    // Call NXTPT.
 
-	//memcpy((byte *)A23D2_ZP_START, (byte *)(0x2ff - A23D2_ZP_LENGTH), A23D2_ZP_LENGTH);  // Put the ZP back.
+	// Save A2-3D2s variables for later.
+	scdMemCpy((byte *)VARS_1_START, (byte *)A23D2_VARS_1_START, A23D2_VARS_1_LENGTH);
+	scdMemCpy((byte *)VARS_2_START, (byte *)A23D2_VARS_2_START, A23D2_VARS_2_LENGTH);
 
-	for (i=0; i<A23D2_ZP_LENGTH; i++) POKE(A23D2_ZP_START + i, PEEK(0x2ff + i));
+	// Restore ZP that A2-3D2 clobbered.
+	scdMemCpy((byte *)COMPILER_ZP_START, (byte *)(SCRATCH_END - COMPILER_ZP_LENGTH), COMPILER_ZP_LENGTH);
 
 	// Restore memory map.
 	POKE(MMU_MEM_BANK_4, 4);
diff --git a/src/a23d2.h b/src/a23d2.h
index 79e5d43..db1e966 100644
--- a/src/a23d2.h
+++ b/src/a23d2.h
@@ -30,6 +30,16 @@ typedef uint8_t byte;
 #endif
 
 
+//#define scdMemCpy  memcpy
+#define scdMemCpy(d,s,l) \
+	({ \
+		volatile byte *dp = (d); \
+		volatile byte *sp = (s); \
+		uint16_t       i  = 0;   \
+		for (i=0; i<(l); i++) *dp++ = *sp++; \
+	})
+
+
 #define A23D2_FAR_BLOCK     42
 #define DATABASE_FAR_BLOCK  43
 
@@ -43,7 +53,7 @@ typedef uint8_t byte;
 
 
 // A2-3D2 Function Addresses.
-#define A23D2_ENTRYS         0x606c
+#define A23D2_ENTRYN         0x6090
 #define A23D2_NXTPT          0x6118
 #define A23D2_SINEX          0x61f6
 #define A23D2_COSEX          0x620f
@@ -52,8 +62,21 @@ typedef uint8_t byte;
 #define A23D2_TEST_DATABASE  0x80fb
 #define A23D2_TDATA          0x613e
 #define A23D2_IBP            0x9b
-#define A23D2_ZP_START       0x60
-#define A23D2_ZP_LENGTH      0x62
+#define A23D2_VARS_1_START   0x7c
+#define A23D2_VARS_1_LENGTH  0x20
+#define A23D2_VARS_2_START   0xbb
+#define A23D2_VARS_2_LENGTH  0x3
+
+// Stuff A2-3D2 is going to clobber that our compiler may want.
+#define COMPILER_ZP_START    0x60  // To 0xC2
+#define COMPILER_ZP_LENGTH   0x62
+
+// Our Scratch Addresses.
+#define CAMERA_SHARED_START  0x200 // To 0x209
+#define CAMERA_SHARED_LENGTH 0x9
+#define VARS_1_START         0x20a // To 0x22a
+#define VARS_2_START         0x22b // To 0x22d
+#define SCRATCH_END          0x2ff
 
 
 // A2-3D1 Commands.  Commented out items are Apple ][ only.
@@ -92,7 +115,7 @@ typedef uint8_t byte;
 #define END    0x79 // End of Database
 
 
-typedef struct cameraS {
+typedef struct cameraS {  // 9 bytes.
 	int16_t x;
 	int16_t y;
 	int16_t z;