diff --git a/src/framebuffer.c b/src/framebuffer.c
index 4185ef1..74bf27c 100644
--- a/src/framebuffer.c
+++ b/src/framebuffer.c
@@ -2,18 +2,14 @@
 // Created by MightyPork on 2022/11/12.
 //
 
-#include "user_interface.h"
 #include "framebuffer.h"
-#include "ssd1306.h"
-
-/* Tiny framebuffer */
-#define FBW DISPLAY_W
-#define FBH DISPLAY_H
 
 #define MIN(a,b) ((a)>(b)?(b):(a))
 #define MAX(a,b) ((a)>(b)?(a):(b))
 
-static uint8_t fb[(FBH/8)*FBW];
+#include <string.h>
+
+uint8_t fb[(FBH / 8) * FBW];
 
 /** Fill with a vertical pattern, 1 byte */
 void fb_fill(uint8_t pattern) {
@@ -245,7 +241,7 @@ void fb_bitmap(uint8_t x, uint8_t y, uint8_t w, uint8_t h, const uint8_t *map, u
 
             // last
             for (uint8_t i = 0; i < w; i++) {
-                uint8_t mask = (map[i + mapc0] & (0xFF << (8 - rowrem))) >> rowrem;
+                uint8_t mask = (map[i + mapc0] & (0xFF << (8 - rowrem))) >> (8 - rowrem);
                 if (color) {
                     fb[cell + i] |= mask;
                 } else {
@@ -260,42 +256,6 @@ void fb_bitmap(uint8_t x, uint8_t y, uint8_t w, uint8_t h, const uint8_t *map, u
             }
             mapc0 += w0;
         }
-
-#if 0
-        // Middle
-        uint8_t whole_cells = h / 8;
-        h -= whole_cells * 8;
-        for(uint8_t j = 0; j < whole_cells; j++) {
-            cell += FBW;
-            mapc0 += w0;
-            for(uint8_t i = 0; i < w; i++) {
-                uint8_t mask = map[i + mapc0];
-                if (color) {
-                    fb[cell + i] |= mask;
-                } else {
-                    fb[cell + i] &= ~mask;
-                }
-            }
-        }
-
-        // last
-        mapc0 += w0;
-        cell += FBW;
-
-        // last
-        for(uint8_t i = 0; i < w; i++) {
-            uint8_t mask = map[i + mapc0] & (0xFF >> (8-h));
-            if (color) {
-                fb[cell + i] |= mask;
-            } else {
-                fb[cell + i] &= ~mask;
-            }
-        }
-#endif
     }
 }
 
-
-void fb_blit() {
-    ssd1306_drawBuffer(0, 0, FBW, FBH, fb);
-}
diff --git a/src/framebuffer.h b/src/framebuffer.h
index b9fdacf..b0dcb44 100644
--- a/src/framebuffer.h
+++ b/src/framebuffer.h
@@ -8,6 +8,24 @@
 #include <stdbool.h>
 #include <stdint.h>
 
+#include "framebuffer_config.h"
+
+#define FBSET   0xFF
+#define FBCLEAR 0x00
+
+/// Framebuffer backing array.
+///
+/// The format is the native format for SSD1306: array of bytes representing pixels in 8 rows at once, LSB is the topmost row.
+///
+/// a0  b0 ... til the display width
+/// a1  b1
+/// a2  b2
+/// ... ...
+/// a7  b7
+///
+/// and more bytes continue rows 8-15 and so on
+extern uint8_t fb[(FBH / 8) * FBW];
+
 void fb_fill(uint8_t pattern);
 void fb_clear(void);
 void fb_px(uint8_t x, uint8_t y, uint8_t color);
@@ -15,6 +33,9 @@ void fb_hline(uint8_t x, uint8_t y, uint8_t w, uint8_t color);
 void fb_vline(uint8_t x, uint8_t y, uint8_t h, uint8_t color);
 void fb_rect(uint8_t x, uint8_t y, uint8_t w, uint8_t h, uint8_t color);
 void fb_bitmap(uint8_t x, uint8_t y, uint8_t w, uint8_t h, const uint8_t *map, uint8_t color);
-void fb_blit(void);
+
+/// Output the framebuffer array `fb` to the display device.
+extern void fb_blit(void);
+
 
 #endif //FRAMEBUFFER_H
diff --git a/src/framebuffer_config.h b/src/framebuffer_config.h
new file mode 100644
index 0000000..56f495e
--- /dev/null
+++ b/src/framebuffer_config.h
@@ -0,0 +1,7 @@
+#ifndef FRAMEBUFFER_CONFIG_H
+#define FRAMEBUFFER_CONFIG_H
+
+#define FBW 128
+#define FBH 32
+
+#endif /* FRAMEBUFFER_CONFIG_H */
diff --git a/src/user_interface.c b/src/user_interface.c
index 483a520..e5be2a0 100644
--- a/src/user_interface.c
+++ b/src/user_interface.c
@@ -8,9 +8,14 @@
 #include "sevenseg.h"
 #include "global_state.h"
 #include "radiation.h"
+#include "framebuffer.h"
 
 static bool ended_loading = false;
 
+void fb_blit() {
+    ssd1306_drawBuffer(0, 0, FBW, FBH, fb);
+}
+
 static struct SevenSeg sseg = {
         .x0 = 0,
         .y0 = 0,