diff --git a/.ccls b/.ccls
new file mode 100644
index 0000000..814530d
--- /dev/null
+++ b/.ccls
@@ -0,0 +1,3 @@
+clang
+%h -x c++-header
+-I/otherhome/john/Amiga/Development/NDKs/3.9/Include/include_h
diff --git a/blitter.c b/blitter.c
new file mode 100644
index 0000000..c6d5cac
--- /dev/null
+++ b/blitter.c
@@ -0,0 +1,226 @@
+#include <stdlib.h>
+#include <hardware/custom.h>
+
+#include "blitter.h"
+#include "system.h"
+#include "types.h"
+
+extern struct Custom far custom;
+
+/**
+ * @param setup Data about the line's draw properties are injected into this struct.
+ */
+void blit_calculateLineBlit(
+  struct BlitDrawLineSetup *setup,
+  uint16_t sx,
+  uint16_t sy,
+  uint16_t ex,
+  uint16_t ey
+) {
+  uint16_t i;
+
+  setup->sx = sx;
+  setup->dx = ex - sx;
+  setup->dy = ey - sy;
+
+  if (setup->dx == 0 && setup->dy == 0) return;
+
+  setup->sud = abs(setup->dy) < abs(setup->dx);
+  if (!setup->sud) { i = setup->dx; setup->dx = setup->dy; setup->dy = i; }
+
+  setup->sul = setup->dy < 0;
+  setup->dy = abs(setup->dy);
+
+  setup->aul = setup->dx < 0;
+  setup->dx = abs(setup->dx);
+
+  setup->accumulator = 4 * setup->dy - 2 * setup->dx;
+  setup->sign = setup->accumulator < 0;
+}
+
+void blit_drawSingleLine(
+  struct BlitAreaDetails *blitAreaDetails,
+  struct BlitDrawLineSetup *setup
+) {
+    custom.bltadat = 0x8000;
+    custom.bltbdat = setup->linePattern;
+
+    custom.bltafwm = 0xffff;
+    custom.bltalwm = 0xffff;
+
+    custom.bltamod = 4 * (setup->dy - setup->dx);
+    custom.bltbmod = 4 * setup->dy;
+    custom.bltcmod = blitAreaDetails->drawAreaWidth / 8;
+    custom.bltdmod = blitAreaDetails->drawAreaWidth / 8;
+
+    custom.bltapt = setup->accumulator;
+    custom.bltcpt = setup->target;
+    custom.bltdpt = setup->target;
+
+    custom.bltcon0 = ((setup->sx % 16) << 12) + (11 << 8) + 0xca;
+    custom.bltcon1 = 1 + (setup->aul << 2) + (setup->sul << 3) + (setup->sud << 4) + (setup->sign << 6);
+
+    custom.bltsize = 0x02 + ((setup->dx + 1) << 6);
+}
+
+void blit_fillAreaDetailsFromScreenSetup(
+  struct ScreenSetup *screenSetup,
+  struct BlitAreaDetails *blitAreaDetails
+) {
+  blitAreaDetails->target = screenSetup->memoryStart;
+  blitAreaDetails->drawAreaWidth = screenSetup->width;
+  blitAreaDetails->nextBitplaneAdvance = screenSetup->nextBitplaneAdvance;
+  blitAreaDetails->contiguousBitplanes = screenSetup->bitplanes;
+}
+
+void blit_drawLine(
+  struct BlitAreaDetails *blitAreaDetails,
+  struct BlitDrawLineSetup *setup,
+  uint16_t sx,
+  uint16_t sy,
+  uint16_t ex,
+  uint16_t ey,
+  uint8_t color
+) {
+  int i;
+
+  blit_calculateLineBlit(setup, sx, sy, ex, ey);
+  setup->target = blitAreaDetails->target + WORD_ALIGNED_BYTE_POSITION(blitAreaDetails->drawAreaWidth, sx, sy);
+
+  for (i = 0; i < blitAreaDetails->contiguousBitplanes; ++i) {
+    setup->linePattern = ((color & 1) == 1) ? 0xffff : 0;
+
+    blit_drawSingleLine(blitAreaDetails, setup);
+
+    setup->target += blitAreaDetails->nextBitplaneAdvance;
+    color >>= 1;
+
+    WaitBlit();
+  }
+}
+
+void blit_copyOneToOne(
+  struct BlitAreaDetails *source,
+  struct BlitAreaDetails *target,
+  uint16_t sx,
+  uint16_t sy,
+  uint16_t ex,
+  uint16_t ey,
+  uint16_t tx,
+  uint16_t ty
+) {
+  uint16_t dx = ex - sx;
+  uint16_t dy = ey - sy;
+
+  // 23 = 2
+  // 24 = 3
+  // 0-15 has to equal 2
+  // 16-31 has to equal 4
+  //
+  // 23 = ((23 / 8) & fffe) + 2 = 
+  uint16_t aModulo = (source->drawAreaWidth / 8) - (((dx + 16) >> 3) & 0xfffe);
+  uint16_t dModulo = (target->drawAreaWidth / 8) - (((dx + 16) >> 3) & 0xfffe);
+
+  uint8_t shiftA = sx % 16;
+
+  unsigned char *aPointer = source->target + WORD_ALIGNED_BYTE_POSITION(source->drawAreaWidth, sx, sy);
+  unsigned char *dPointer = target->target + WORD_ALIGNED_BYTE_POSITION(target->drawAreaWidth, tx, ty);
+
+  custom.bltcon0 = (1 << 11) + (1 << 8) + 0xca;
+  custom.bltcon1 = (1 << 1);
+  //custom.bltapt = aPointer;
+  //custom.bltdpt = dPointer;
+
+  custom.bltapt = aPointer + WORD_ALIGNED_BYTE_POSITION(source->drawAreaWidth, dx, dy);
+  custom.bltdpt = dPointer + WORD_ALIGNED_BYTE_POSITION(target->drawAreaWidth, dx, dy);
+
+  custom.bltamod = aModulo;
+  custom.bltdmod = dModulo;
+  custom.bltafwm = 0xffff;
+  custom.bltalwm = 0xffff;
+
+  custom.bltsize = (dx / 16) + 1 + (dy << 6);
+}
+
+void blit_howDoesFWMandLWMWork(
+  struct BlitAreaDetails *target
+) {
+  // data in a
+  // setting fwm and lwm to mask that
+
+  // dma enabled for only D
+  custom.bltcon0 = 0xF0 + (1 << 8);
+  custom.bltcon1 = 0;
+
+  custom.bltadat = 0xffff;
+  custom.bltafwm = 0x0ff0;
+  custom.bltalwm = 0xf0f0;
+
+  custom.bltdpt = target->target;
+  custom.bltamod = 0;
+  custom.bltbmod = 0;
+
+  custom.bltsize = (2) + (1 << 6);
+}
+
+// TODO: blit_drawRectangle
+void blit_clearScreen(struct ScreenSetup *screenSetup, int color) {
+  unsigned char *target = screenSetup->memoryStart;
+  int i;
+
+  // a is source
+  // b is mask
+  // c is background
+  // d is destination
+
+  // so I want AB+`AC
+
+  custom.bltcon0 = (0x01 << 8) + 0xf0;
+  custom.bltcon1 = 0;
+  custom.bltamod = 0;
+  custom.bltdmod = 0;
+  custom.bltafwm = 0xffff;
+  custom.bltalwm = 0xffff;
+
+  for (i = 0; i < screenSetup->bitplanes; ++i) {
+    custom.bltadat = color & 1 == 1 ? 0xffff : 0;
+    custom.bltdpt = target + (320 * 256 / 8) * i;
+    custom.bltsize = (256 << 7) + (320 / 8);
+    myWaitBlit();
+
+    color >>= 1;
+  }
+}
+
+void blit_fillPolygon(
+  struct ScreenSetup *screenSetup,
+  uint16_t sx,
+  uint16_t sy,
+  uint16_t ex,
+  uint16_t ey,
+  uint8_t color
+) {
+  // use a standard copy blit
+  // set bltadat to 0xffff
+  // set bltdpt to the top left corner of the zone
+  // width is dx / 8
+  // height is dy
+  // enable descending mode
+  // enable inclusive fill for now
+
+  uint16_t dx = ex - sx;
+  uint16_t dy = ey - sy;
+
+  unsigned char *source = screenSetup->memoryStart + ((((ey * screenSetup->width + ex) >> 3) - 2) & 0xfffe);
+  unsigned char *target = screenSetup->memoryStart + (((((ey + 100) * screenSetup->width + ex) >> 3) - 2) & 0xfffe);
+
+  custom.bltcon0 = (1 << 11) + (1 << 8) + 0xF0; // we don't want to copy anything so we only enable target
+  custom.bltcon1 = (1 << 1) + (1 << 3);
+  custom.bltapt = source;
+  custom.bltdpt = target;
+  custom.bltamod = ((screenSetup->width - dx) >> 3) + 1;
+  custom.bltdmod = ((screenSetup->width - dx) >> 3) + 1;
+  custom.bltafwm = 0xffff;
+  custom.bltalwm = 0xffff;
+  custom.bltsize = (dx / 16) + (dy << 6);
+}
diff --git a/blitter.h b/blitter.h
new file mode 100644
index 0000000..68da825
--- /dev/null
+++ b/blitter.h
@@ -0,0 +1,62 @@
+#ifndef __BLITTER_H__
+#define __BLITTER_H__
+
+#include "types.h"
+#include "screen.h"
+
+#define WORD_ALIGNED_BYTE_POSITION(width, x, y) (((width * y + x) >> 3) & 0xfffe)
+
+struct BlitAreaDetails {
+  unsigned char *target;
+  uint16_t drawAreaWidth;
+  uint16_t nextBitplaneAdvance;
+  uint8_t contiguousBitplanes;
+};
+
+struct BlitDrawLineSetup {
+  uint16_t linePattern;
+  unsigned char *target;
+
+  int dx, dy, sx;
+  int sud, sul, aul, accumulator, sign;
+};
+
+void blit_fillAreaDetailsFromScreenSetup(
+  struct ScreenSetup *screenSetup,
+  struct BlitAreaDetails *blitAreaDetails
+);
+
+void blit_calculateLineBlit(
+  struct BlitDrawLineSetup *setup,
+  uint16_t sx,
+  uint16_t sy,
+  uint16_t ex,
+  uint16_t ey
+);
+
+void blit_drawLine(
+  struct BlitAreaDetails *blitAreaDetails,
+  struct BlitDrawLineSetup *setup,
+  uint16_t sx,
+  uint16_t sy,
+  uint16_t ex,
+  uint16_t ey,
+  uint8_t color
+);
+
+void blit_copyOneToOne(
+  struct BlitAreaDetails *source,
+  struct BlitAreaDetails *target,
+  uint16_t sx,
+  uint16_t sy,
+  uint16_t ex,
+  uint16_t ey,
+  uint16_t tx,
+  uint16_t ty
+);
+
+void blit_howDoesFWMandLWMWork(
+  struct BlitAreaDetails *target
+);
+
+#endif
diff --git a/copper.c b/copper.c
new file mode 100644
index 0000000..1d5711a
--- /dev/null
+++ b/copper.c
@@ -0,0 +1,27 @@
+#include "copper.h"
+#include "system.h"
+
+#include <clib/exec_protos.h>
+#include <exec/memory.h>
+#include <hardware/custom.h>
+
+extern struct Custom far custom;
+
+uint16_t * prepareNewCopperlist(void) {
+  uint16_t *copperlist = AllocMem(
+    COPPERLIST_SIZE,
+    MEMF_CHIP | MEMF_CLEAR
+  );
+
+  initializeCopperlist(copperlist);
+
+  return copperlist;
+}
+
+void setCopperlist(uint16_t *copperlist) {
+  custom.cop1lc = copperlist;
+}
+
+void freeCopperlist(uint16_t *copperlist) {
+  FreeMem(copperlist, COPPERLIST_SIZE);
+}
diff --git a/copper.h b/copper.h
new file mode 100644
index 0000000..8285d2e
--- /dev/null
+++ b/copper.h
@@ -0,0 +1,12 @@
+#ifndef __COPPER_H__
+#define __COPPER_H__
+
+#define COPPERLIST_SIZE (10000)
+
+#include "types.h"
+
+uint16_t * prepareNewCopperlist(void);
+void setCopperlist(uint16_t *copperlist);
+void freeCopperlist(uint16_t *copperlist);
+
+#endif
diff --git a/main b/main
index a617893..5695407 100755
Binary files a/main and b/main differ
diff --git a/main.c b/main.c
index aedf711..67a4718 100644
--- a/main.c
+++ b/main.c
@@ -7,285 +7,108 @@
 #include <hardware/custom.h>
 #include <hardware/dmabits.h>
 
+#include "blitter.h"
+#include "copper.h"
+#include "screen.h"
+#include "types.h"
+#include "system.h"
+
 extern struct Custom far custom;
 
-struct ScreenSetup {
-  short int width;
-  short int height;
-  short int bitplanes;
-  unsigned char *memoryStart;
-};
-
-typedef UWORD color_t;
-
-extern void TakeOverSystem(void);
-extern void GiveBackSystem(void);
-extern void InitializeCopperlist(void *);
-extern void SetUpDisplay(struct ScreenSetup *);
-extern UWORD* AddDisplayToCopperlist(UWORD *copperlist, struct ScreenSetup *);
-extern UWORD* AddColorsToCopperlist(UWORD *copperlist, color_t[], int count);
-extern UWORD* EndCopperlist(UWORD *copperlist);
-
-#define SCREEN_WIDTH (320)
-#define SCREEN_HEIGHT (256)
-
-#define TOTAL_SCREEN_SETUP_SIZE(s) ((s->width / 8) * s->height * s->bitplanes)
-
-void AllocateScreenMemory(struct ScreenSetup *screenSetup) {
-  char *memory = (char *)AllocMem(
-    TOTAL_SCREEN_SETUP_SIZE(screenSetup),
-    MEMF_CLEAR | MEMF_CHIP
-  );
-
-  screenSetup->memoryStart = memory;
-}
-
-void FreeScreenMemory(struct ScreenSetup *screenSetup) {
-  FreeMem(
-    screenSetup->memoryStart,
-    TOTAL_SCREEN_SETUP_SIZE(screenSetup)
-  );
-}
-
-#define COPPERLIST_SIZE (10000)
-
-UWORD * PrepareNewCopperlist(void) {
-  UWORD *copperlist = AllocMem(
-    COPPERLIST_SIZE,
-    MEMF_CHIP | MEMF_CLEAR
-  );
-
-  InitializeCopperlist(copperlist);
-
-  return copperlist;
-}
-
-void SetCopperlist(UWORD *copperlist) {
-  custom.cop1lc = (ULONG)copperlist;
-}
-
-void FreeCopperlist(UWORD *copperlist) {
-  FreeMem(copperlist, COPPERLIST_SIZE);
-}
-
-void WriteSomethingToScreen(struct ScreenSetup *screenSetup) {
+void writeSomethingToScreen(struct ScreenSetup *screenSetup) {
   *(screenSetup->memoryStart) = 255;
   *(screenSetup->memoryStart + 8) = 0xAA;
   *(screenSetup->memoryStart + 16) = 0xF0;
   *(screenSetup->memoryStart + SCREEN_WIDTH * SCREEN_HEIGHT / 8 + 4) = 255;
 }
 
-void BlitFirstPlaneFirstRowToSecondRow(struct ScreenSetup *screenSetup) {
-  unsigned char *source = screenSetup->memoryStart;
-  unsigned char *target = (screenSetup->memoryStart + SCREEN_WIDTH * 2 / 8);
-
-  // copy a to d
-  // $09F0
-  custom.bltcon0 = 0x09f0;
-  custom.bltcon1 = 0;
-  custom.bltapt = source;
-  custom.bltdpt = target;
-  custom.bltamod = 0;
-  custom.bltdmod = 0;
-  custom.bltafwm = 0xffff;
-  custom.bltalwm = 0xffff;
-  custom.bltsize = 0x0041;
-}
-
-void BlitShiftFirstPlaneFirstRowToThirdRow(struct ScreenSetup *screenSetup) {
-  unsigned char *source = screenSetup->memoryStart;
-  unsigned char *target = (screenSetup->memoryStart + SCREEN_WIDTH * 4 / 8);
-
-  custom.bltcon0 = 0x49f0;
-  custom.bltcon1 = 0;
-  custom.bltapt = source;
-  custom.bltdpt = target;
-  custom.bltamod = 0;
-  custom.bltdmod = 0;
-  custom.bltafwm = 0xffff;
-  custom.bltalwm = 0xffff;
-  custom.bltsize = 0x0041;
-}
-
-void BlitWithMaskInBChannel(struct ScreenSetup *screenSetup) {
-  unsigned char *source = screenSetup->memoryStart;
-  unsigned char *target = (screenSetup->memoryStart + SCREEN_WIDTH * 6 / 8);
-  unsigned char *mask = (screenSetup->memoryStart + 8);
-
-  // a is source
-  // b is mask
-  // d is destination
-
-  // so I want AB
-
-  custom.bltcon0 = 0x0dc0;
-  custom.bltcon1 = 0;
-  custom.bltapt = mask;
-  custom.bltbpt = source;
-  custom.bltdpt = target;
-  custom.bltamod = 0;
-  custom.bltdmod = 0;
-  custom.bltafwm = 0xffff;
-  custom.bltalwm = 0xffff;
-  custom.bltsize = 0x0041;
-}
-
-void BlitWithMaskInBDataInCChannel(struct ScreenSetup *screenSetup) {
-  unsigned char *source = screenSetup->memoryStart;
-  unsigned char *target = (screenSetup->memoryStart + SCREEN_WIDTH * 8 / 8);
-  unsigned char *mask = (screenSetup->memoryStart + 8);
-  unsigned char *background = (screenSetup->memoryStart + 16);
-
-  // a is source
-  // b is mask
-  // c is background
-  // d is destination
-
-  // so I want AB+`AC
-
-  custom.bltcon0 = 0x0fca;
-  custom.bltcon1 = 0;
-  custom.bltapt = mask;
-  custom.bltbpt = source;
-  custom.bltcpt = background;
-  custom.bltdpt = target;
-  custom.bltamod = 0;
-  custom.bltbmod = 0;
-  custom.bltcmod = SCREEN_WIDTH / 8;
-  custom.bltdmod = SCREEN_WIDTH / 8;
-  custom.bltafwm = 0xffff;
-  custom.bltalwm = 0xffff;
-  custom.bltsize = 0x0041;
-}
-
-void BlitDrawHorizontalLine(struct ScreenSetup *screenSetup) {
-
-  // i want to draw a line from 20,20 to 50,80
-  // i need to get dx and dy
-  // dx is 30, dy is 60
-  // the shift value is 20 mod 15 = 5
-  // a data register gets $8000
-  // b data register gets $ffff
-  // text shift is 0
-  // c and d pointers get the word containing the first pixel, so
-  //   screenSetup->memoryStart + 320 * 20 / 8 + 2
-  // module registers get width of bitplane in bytes
-  // blit height is dx + 1 so 31
-  // blit width = 2
-  // logic is ab+'a, so 6, 7, 2, 3, 1, 0
-
-  char *target = screenSetup->memoryStart + (320 * 20 + 20) / 8;
-  int dx = 10;
-  int dy = 60;
-  int tmp;
-
-  if (dx < dy) {
-    tmp = dx;
-    dx = dy;
-    dy = tmp;
-  }
-
-  custom.bltcon0 = (5 << 12) + (11 << 8) + 0xca;
-  custom.bltcon1 = 1;
-  custom.bltapt = 4 * dy - 2 * dx;
-  custom.bltadat = 0x8000;
-  custom.bltbdat = 0xffff;
-  custom.bltcpt = target;
-  custom.bltdpt = target;
-  custom.bltamod = 4 * (dy - dx);
-  custom.bltbmod = 4 * dy;
-  custom.bltcmod = 320 / 8;
-  custom.bltdmod = 320 / 8;
-  custom.bltafwm = 0xffff;
-  custom.bltalwm = 0xffff;
-  custom.bltsize = 0x02 + (dx + 1 << 7);
-}
-
-void BlitClearScreen(struct ScreenSetup *screenSetup, int color) {
-  unsigned char *target = screenSetup->memoryStart;
-  int i;
-
-  // a is source
-  // b is mask
-  // c is background
-  // d is destination
-
-  // so I want AB+`AC
-
-  for (i = 0; i < screenSetup->bitplanes; ++i) {
-    custom.bltcon0 = (0x01 << 8) + 0xf0;
-    custom.bltcon1 = 0;
-    custom.bltadat = color & 1 == 1 ? 0xffff : 0;
-    custom.bltdpt = target + (320 * 256 / 8) * i;
-    custom.bltamod = 0;
-    custom.bltdmod = 0;
-    custom.bltafwm = 0xffff;
-    custom.bltalwm = 0xffff;
-    custom.bltsize = (256 << 7) + (320 / 8);
-
-    color >>= 1;
-    WaitBlit();
-  }
-}
-
 int main(void) {
-  struct ScreenSetup screenSetup = { SCREEN_WIDTH, SCREEN_HEIGHT, 4, 0 };
-  struct ScreenSetup *s = &screenSetup;
-  UWORD *copperlist, *currentCopperlist;
+  struct ScreenSetup screenSetup;
+  uint16_t *copperlist, *currentCopperlist;
   int i, result;
   color_t colors[16];
 
+  struct BlitDrawLineSetup setup;
+  struct BlitAreaDetails blitAreaDetails, sourceBlitCopyDetails;
+
+  unsigned char *polygonScratchArea;
+
   colors[0] = 0x0200;
   colors[1] = 0x0f00;
   colors[2] = 0x0f0f;
   colors[3] = 0x000f;
 
-  SetUpDisplay(&screenSetup);
+  prepareScreen(&screenSetup, SCREEN_WIDTH, SCREEN_HEIGHT, 4);
+  allocateScreenMemory(&screenSetup);
 
-  AllocateScreenMemory(&screenSetup);
-  WriteSomethingToScreen(&screenSetup);
+  blit_fillAreaDetailsFromScreenSetup(
+    &screenSetup,
+    &blitAreaDetails
+  );
+
+  blit_fillAreaDetailsFromScreenSetup(
+    &screenSetup,
+    &sourceBlitCopyDetails
+  );
+
+  polygonScratchArea = AllocMem(SCREEN_WIDTH * SCREEN_HEIGHT / 8, MEMF_CHIP | MEMF_CLEAR);
 
   // blitter copy the first bitplane row down to the second
 
-  copperlist = PrepareNewCopperlist();
+  copperlist = prepareNewCopperlist();
 
-  TakeOverSystem();
+  takeOverSystem();
+
+  setCopperlist(copperlist);
+  setUpDisplay(&screenSetup);
+
+  currentCopperlist = addDisplayToCopperlist(copperlist, &screenSetup);
+  currentCopperlist = addColorsToCopperlist(currentCopperlist, colors, 16);
+  endCopperlist(currentCopperlist);
+
+  // blit a line to the scratch area
+  // blit the scratch area over
 
   /*
-  BlitFirstPlaneFirstRowToSecondRow(&screenSetup);
-  WaitBlit();
-  BlitShiftFirstPlaneFirstRowToThirdRow(&screenSetup);
-  WaitBlit();
-  BlitWithMaskInBChannel(&screenSetup);
-  WaitBlit();
-  BlitWithMaskInBDataInCChannel(&screenSetup);
-  WaitBlit();
-  BlitDrawHorizontalLine(&screenSetup);
+  blit_drawLine(&blitAreaDetails, &setup, 0, 0, 0, 40, 1);
+  blit_drawLine(&blitAreaDetails, &setup, 1, 0, 1, 40, 3);
+  blit_drawLine(&blitAreaDetails, &setup, 15, 0, 15, 40, 3);
+  */
+  //blit_drawLine(&blitAreaDetails, &setup, 16, 10, 16, 40, 3);
+  //blit_drawLine(&blitAreaDetails, &setup, 50, 10, 50, 40, 1);
+  //blit_drawLine(&blitAreaDetails, &setup, 79, 80, 79, 120, 3);
+
+  blit_howDoesFWMandLWMWork(&blitAreaDetails);
+
   WaitBlit();
+
+  /*
+
+
+  blit_copyOneToOne(
+    &blitAreaDetails,
+    &blitAreaDetails,
+    1, 0, 24, 16, 80, 80
+  );
   */
 
-  BlitClearScreen(&screenSetup, 2);
-  WaitBlit();
-
-  SetCopperlist(copperlist);
-
-  SetUpDisplay(&screenSetup);
-
-  currentCopperlist = AddDisplayToCopperlist(copperlist, &screenSetup);
-  currentCopperlist = AddColorsToCopperlist(currentCopperlist, colors, 16);
-  EndCopperlist(currentCopperlist);
-
-  for (i = 0; i < 100; ++i) {
+  for (i = 0; i < 200; ++i) {
     WaitTOF();
   }
 
-  GiveBackSystem();
+  giveBackSystem();
 
-  FreeScreenMemory(&screenSetup);
+  freeScreenMemory(&screenSetup);
 
-  FreeCopperlist(copperlist);
+  freeCopperlist(copperlist);
+  FreeMem(polygonScratchArea, SCREEN_WIDTH * SCREEN_HEIGHT / 8);
 
   printf("Hello from C\n");
 
+  printf("%d %d\n", setup.dx, setup.dy);
+  printf("%d %d %d\n", setup.sud, setup.sul, setup.aul);
+
+  printf("%d %d\n", setup.accumulator, setup.sign);
+
   return 0;
 }
diff --git a/other_blitter.c b/other_blitter.c
new file mode 100644
index 0000000..fe48286
--- /dev/null
+++ b/other_blitter.c
@@ -0,0 +1,124 @@
+void BlitFirstPlaneFirstRowToSecondRow(struct ScreenSetup *screenSetup) {
+  unsigned char *source = screenSetup->memoryStart;
+  unsigned char *target = (screenSetup->memoryStart + SCREEN_WIDTH * 2 / 8);
+
+  custom.bltcon0 = 0x09f0;
+  custom.bltcon1 = 0;
+  custom.bltapt = source;
+  custom.bltdpt = target;
+  custom.bltamod = 0;
+  custom.bltdmod = 0;
+  custom.bltafwm = 0xffff;
+  custom.bltalwm = 0xffff;
+  custom.bltsize = 0x0041;
+}
+
+void BlitShiftFirstPlaneFirstRowToThirdRow(struct ScreenSetup *screenSetup) {
+  unsigned char *source = screenSetup->memoryStart;
+  unsigned char *target = (screenSetup->memoryStart + SCREEN_WIDTH * 4 / 8);
+
+  custom.bltcon0 = 0x49f0;
+  custom.bltcon1 = 0;
+  custom.bltapt = source;
+  custom.bltdpt = target;
+  custom.bltamod = 0;
+  custom.bltdmod = 0;
+  custom.bltafwm = 0xffff;
+  custom.bltalwm = 0xffff;
+  custom.bltsize = 0x0041;
+}
+
+void BlitWithMaskInBChannel(struct ScreenSetup *screenSetup) {
+  unsigned char *source = screenSetup->memoryStart;
+  unsigned char *target = (screenSetup->memoryStart + SCREEN_WIDTH * 6 / 8);
+  unsigned char *mask = (screenSetup->memoryStart + 8);
+
+  // a is source
+  // b is mask
+  // d is destination
+
+  // so I want AB
+
+  custom.bltcon0 = 0x0dc0;
+  custom.bltcon1 = 0;
+  custom.bltapt = mask;
+  custom.bltbpt = source;
+  custom.bltdpt = target;
+  custom.bltamod = 0;
+  custom.bltdmod = 0;
+  custom.bltafwm = 0xffff;
+  custom.bltalwm = 0xffff;
+  custom.bltsize = 0x0041;
+}
+
+void BlitWithMaskInBDataInCChannel(struct ScreenSetup *screenSetup) {
+  unsigned char *source = screenSetup->memoryStart;
+  unsigned char *target = (screenSetup->memoryStart + SCREEN_WIDTH * 8 / 8);
+  unsigned char *mask = (screenSetup->memoryStart + 8);
+  unsigned char *background = (screenSetup->memoryStart + 16);
+
+  // a is source
+  // b is mask
+  // c is background
+  // d is destination
+
+  // so I want AB+`AC
+
+  custom.bltcon0 = 0x0fca;
+  custom.bltcon1 = 0;
+  custom.bltapt = mask;
+  custom.bltbpt = source;
+  custom.bltcpt = background;
+  custom.bltdpt = target;
+  custom.bltamod = 0;
+  custom.bltbmod = 0;
+  custom.bltcmod = SCREEN_WIDTH / 8;
+  custom.bltdmod = SCREEN_WIDTH / 8;
+  custom.bltafwm = 0xffff;
+  custom.bltalwm = 0xffff;
+  custom.bltsize = 0x0041;
+}
+
+void BlitDrawHorizontalLine(struct ScreenSetup *screenSetup) {
+
+  // i want to draw a line from 20,20 to 50,80
+  // i need to get dx and dy
+  // dx is 30, dy is 60
+  // the shift value is 20 mod 15 = 5
+  // a data register gets $8000
+  // b data register gets $ffff
+  // text shift is 0
+  // c and d pointers get the word containing the first pixel, so
+  //   screenSetup->memoryStart + 320 * 20 / 8 + 2
+  // module registers get width of bitplane in bytes
+  // blit height is dx + 1 so 31
+  // blit width = 2
+  // logic is ab+'a, so 6, 7, 2, 3, 1, 0
+
+  char *target = screenSetup->memoryStart + (320 * 20 + 20) / 8;
+  int dx = 10;
+  int dy = 60;
+  int tmp;
+
+  if (dx < dy) {
+    tmp = dx;
+    dx = dy;
+    dy = tmp;
+  }
+
+  custom.bltcon0 = (5 << 12) + (11 << 8) + 0xca;
+  custom.bltcon1 = 1;
+  custom.bltapt = 4 * dy - 2 * dx;
+  custom.bltadat = 0x8000;
+  custom.bltbdat = 0xffff;
+  custom.bltcpt = target;
+  custom.bltdpt = target;
+  custom.bltamod = 4 * (dy - dx);
+  custom.bltbmod = 4 * dy;
+  custom.bltcmod = 320 / 8;
+  custom.bltdmod = 320 / 8;
+  custom.bltafwm = 0xffff;
+  custom.bltalwm = 0xffff;
+  custom.bltsize = 0x02 + (dx + 1 << 7);
+}
+
diff --git a/screen.c b/screen.c
new file mode 100644
index 0000000..76ff954
--- /dev/null
+++ b/screen.c
@@ -0,0 +1,33 @@
+#include "screen.h"
+#include "types.h"
+
+#include <clib/exec_protos.h>
+#include <exec/memory.h>
+
+void allocateScreenMemory(struct ScreenSetup *screenSetup) {
+  char *memory = (char *)AllocMem(
+    TOTAL_SCREEN_SETUP_SIZE(screenSetup),
+    MEMF_CLEAR | MEMF_CHIP
+  );
+
+  screenSetup->memoryStart = memory;
+}
+
+void freeScreenMemory(struct ScreenSetup *screenSetup) {
+  FreeMem(
+    screenSetup->memoryStart,
+    TOTAL_SCREEN_SETUP_SIZE(screenSetup)
+  );
+}
+
+void prepareScreen(
+  struct ScreenSetup *screenSetup,
+  uint16_t width,
+  uint16_t height,
+  uint8_t bitplanes
+) {
+  screenSetup->width = width;
+  screenSetup->height = height;
+  screenSetup->bitplanes = bitplanes;
+  screenSetup->nextBitplaneAdvance = width * height / 8;
+}
diff --git a/screen.h b/screen.h
new file mode 100644
index 0000000..597622e
--- /dev/null
+++ b/screen.h
@@ -0,0 +1,29 @@
+#ifndef __SCREEN_H__
+#define __SCREEN_H__
+
+#include "types.h"
+
+struct ScreenSetup {
+  short int width;
+  short int height;
+  short int bitplanes;
+  unsigned char *memoryStart;
+  short int nextBitplaneAdvance;
+};
+
+
+#define SCREEN_WIDTH (320)
+#define SCREEN_HEIGHT (256)
+
+#define TOTAL_SCREEN_SETUP_SIZE(s) ((s->width / 8) * s->height * s->bitplanes)
+
+void allocateScreenMemory(struct ScreenSetup *screenSetup);
+void freeScreenMemory(struct ScreenSetup *screenSetup);
+void prepareScreen(
+  struct ScreenSetup *screenSetup,
+  uint16_t width,
+  uint16_t height,
+  uint8_t bitplanes
+);
+
+#endif
diff --git a/smakefile b/smakefile
index d03ec97..0cbc79e 100644
--- a/smakefile
+++ b/smakefile
@@ -6,5 +6,5 @@ all: main
 .s.o:
 	genam -l $*.s
 
-main: main.o blitter.o
-	sc link to main main.o blitter.o
+main: main.o system.o blitter.o screen.o copper.o
+	sc link to main main.o system.o blitter.o screen.o copper.o
diff --git a/system.h b/system.h
new file mode 100644
index 0000000..f9c868b
--- /dev/null
+++ b/system.h
@@ -0,0 +1,21 @@
+#ifndef __SYSTEM_H__
+#define __SYSTEM_H__
+
+#include "types.h"
+#include "screen.h"
+
+// this needs to be kept in sync with the XDEFs in system.s
+
+// copperlist
+extern void initializeCopperlist(void *copperlist);
+extern uint16_t* endCopperlist(uint16_t *copperlist);
+extern uint16_t* addDisplayToCopperlist(uint16_t *copperlist, struct ScreenSetup *);
+extern uint16_t* addColorsToCopperlist(uint16_t *copperlist, color_t[], int count);
+
+extern void takeOverSystem(void);
+extern void giveBackSystem(void);
+extern void setUpDisplay(struct ScreenSetup *);
+
+extern void myWaitBlit(void);
+
+#endif
diff --git a/blitter.s b/system.s
similarity index 86%
rename from blitter.s
rename to system.s
index 22d2c51..6d75809 100644
--- a/blitter.s
+++ b/system.s
@@ -1,10 +1,11 @@
-  XDEF _TakeOverSystem
-  XDEF _GiveBackSystem
-  XDEF _InitializeCopperlist
-  XDEF _SetUpDisplay
-  XDEF _AddDisplayToCopperlist
-  XDEF _AddColorsToCopperlist
-  XDEF _EndCopperlist
+  XDEF _takeOverSystem
+  XDEF _giveBackSystem
+  XDEF _initializeCopperlist
+  XDEF _setUpDisplay
+  XDEF _addDisplayToCopperlist
+  XDEF _addColorsToCopperlist
+  XDEF _endCopperlist
+  XDEF _myWaitBlit
 
   XREF _custom
 
@@ -24,7 +25,7 @@ FUNC_CNT SET FUNC_CNT-6
   INCLUDE "hardware/custom.i"
   INCLUDE "hardware/dmabits.i"
 
-; @param 1 Pointer to numm terminated name of library
+; @param 1 Pointer to null terminated name of library
 ; @param 2 Minimum version of library, 0 for any
 ; @outreg D0 pointer to library in memory
 OpenLibrary MACRO
@@ -59,7 +60,7 @@ RestoreRegister MACRO
 
 BPLCON0_COLOR EQU $200
 
-_TakeOverSystem:
+_takeOverSystem:
   MOVE.L A6,-(SP)
     OpenLibrary #GraphicsLibrary,#0
     MOVE.L D0,GraphicsBase
@@ -94,7 +95,7 @@ _TakeOverSystem:
   MOVE.L (SP)+,A6
   RTS
 
-_GiveBackSystem:
+_giveBackSystem:
   MOVE.L A6,-(SP)
     LEA _custom,A0
 
@@ -118,7 +119,7 @@ _GiveBackSystem:
   RTS
 
 ; @stack *copperlist Pointer to copperlist
-_InitializeCopperlist:
+_initializeCopperlist:
   MOVE.L 4(A7),A0
   MOVE.L #$FFFFFFFE,(A0)
 
@@ -126,7 +127,7 @@ _InitializeCopperlist:
 
 ; @stack *copperlist Pointer to copperlist
 ; @stack ScreenSetup Pointer to screensetup struct
-_AddDisplayToCopperlist:
+_addDisplayToCopperlist:
   MOVE.L 4(A7),A0 ; copperlist
   MOVE.L 8(A7),A1 ; struct
 
@@ -154,16 +155,18 @@ _AddDisplayToCopperlist:
     MULU D2,D3
     ADD.L A2,D3
 
-    ; low
+    ; high byte
     SWAP D3
     MOVE.W D1,(A0)+
     MOVE.W D3,(A0)+
-    ; high
+    ; low byte
     SWAP D3
     ADDQ #2,D1
     MOVE.W D1,(A0)+
     MOVE.W D3,(A0)+
     DBRA D0,.continue
+
+    ; current copperlist position
     MOVE.L A0,D0
   MOVEM.L (SP)+,A2/D2/D3
 
@@ -171,8 +174,8 @@ _AddDisplayToCopperlist:
 
 ; @stack *copperlist
 ; @stack *colors
-; @stach count
-_AddColorsToCopperlist:
+; @stack count
+_addColorsToCopperlist:
   MOVE.L 4(A7),A0 ; copperlist
   MOVE.L 8(A7),A1 ; colors
   MOVE.L 12(A7),D0 ; count
@@ -192,7 +195,7 @@ _AddColorsToCopperlist:
   RTS
 
 ; @stack *copperlist
-_EndCopperlist:
+_endCopperlist:
   MOVE.L 4(A7),A0
 
   MOVE.W #$ffff,(A0)+
@@ -202,7 +205,7 @@ _EndCopperlist:
   RTS
 
 ; @stack *ScreenSetup
-_SetUpDisplay:
+_setUpDisplay:
   MOVE.L 4(A7),A0
 
   LEA _custom,A1
@@ -226,6 +229,20 @@ _SetUpDisplay:
 
   RTS
 
+_myWaitBlit:
+  LEA _custom,A0
+
+  BTST.B #DMAB_BLTDONE-8,dmaconr(A0)
+  BTST.B #DMAB_BLTDONE-8,dmaconr(A0)
+  BEQ .done
+
+.loop:
+  BTST.B #DMAB_BLTDONE-8,dmaconr(A0)
+  BNE .loop
+
+.done:
+  RTS
+
   CNOP 0,4
 OldView dc.l 0
 OldCopper dc.l 0
diff --git a/types.h b/types.h
new file mode 100644
index 0000000..6e14f83
--- /dev/null
+++ b/types.h
@@ -0,0 +1,11 @@
+#ifndef __TYPES_H__
+#define __TYPES_H__
+
+#include <exec/types.h>
+
+typedef unsigned short color_t;
+typedef unsigned short uint16_t;
+typedef unsigned char uint8_t;
+typedef signed char int8_t;
+
+#endif