diff --git a/implementations/uvm-ncc/font/convert.py b/implementations/uvm-ncc/font/convert.py
index 597c50c..9dcf906 100644
--- a/implementations/uvm-ncc/font/convert.py
+++ b/implementations/uvm-ncc/font/convert.py
@@ -22,8 +22,9 @@ for i, _ in enumerate(txt):
 
 print(f'''\
 
-int font_{font_name}_{pointsize}_width = {w};
-int font_{font_name}_{pointsize}_height = {h};
+u64 font_{font_name}_{pointsize}_number_of_characters = {len(txt)};
+u64 font_{font_name}_{pointsize}_width = {w};
+u64 font_{font_name}_{pointsize}_height = {h};
 
 u32 font_{font_name}_{pointsize}_data[{len(txt)}][{w * h}];
 
diff --git a/implementations/uvm-ncc/font/font.h b/implementations/uvm-ncc/font/font.h
index 488dfba..9929a11 100644
--- a/implementations/uvm-ncc/font/font.h
+++ b/implementations/uvm-ncc/font/font.h
@@ -1,6 +1,7 @@
 
-int font_Inconsolata_22_width = 12;
-int font_Inconsolata_22_height = 25;
+u64 font_Inconsolata_22_number_of_characters = 94;
+u64 font_Inconsolata_22_width = 12;
+u64 font_Inconsolata_22_height = 25;
 
 u32 font_Inconsolata_22_data[94][300];
 
diff --git a/implementations/uvm-ncc/graphics.h b/implementations/uvm-ncc/graphics.h
index 47a36ad..c39d502 100644
--- a/implementations/uvm-ncc/graphics.h
+++ b/implementations/uvm-ncc/graphics.h
@@ -1,3 +1,4 @@
+#include <stddef.h>
 
 void
 draw_background(u32* buffer, size_t w, size_t h)
@@ -12,3 +13,32 @@ draw_background(u32* buffer, size_t w, size_t h)
 		}
 	}
 }
+
+void
+carefree_alpha_blend_blit(u32* dest, u32* source, size_t dest_stride, u64 dest_x, u64 dest_y, u64 w, u64 h)
+{
+	u32* d = dest + dest_stride * dest_y + dest_x;
+	for (u64 x = 0; x < w; ++x) {
+		for (u64 y = 0; y < h; ++y) {
+			u32* pix_ptr = d + x + dest_stride * y;
+			u32* spix_ptr = source + x + w * y;
+			u32 pixel = *spix_ptr;
+			u8 alpha = pixel >> 24;
+			if (!alpha) {  // no alpha
+				continue;
+			}
+			if (0xFF == alpha) {
+				*pix_ptr = pixel;
+				continue;
+			}
+			u32 dest_pixel = *pix_ptr;
+			u8 unalpha = 0xFF - alpha;
+			u8 red = (((dest_pixel >> 16) & 255) * unalpha + ((pixel >> 16) & 255) * alpha) / 0xff;
+			u8 green = (((dest_pixel >> 8) & 255) * unalpha + ((pixel >> 8) & 255) * alpha) / 0xff;
+			u8 blue = ((dest_pixel & 255) * unalpha + (pixel & 255) * alpha) / 0xff;
+			*pix_ptr = (alpha << 24) | (red << 16) | (green << 8) | blue;
+		}
+	}
+}
+
+
diff --git a/implementations/uvm-ncc/xerblin.c b/implementations/uvm-ncc/xerblin.c
index a2c9686..d3a3cbe 100644
--- a/implementations/uvm-ncc/xerblin.c
+++ b/implementations/uvm-ncc/xerblin.c
@@ -1,3 +1,4 @@
+#include <stdlib.h>
 #include <uvm/syscalls.h>
 #include <uvm/utils.h>
 #include "/home/sforman/src/Joypy/implementations/uvm-ncc/font/font.h"
@@ -10,34 +11,33 @@ size_t FRAME_WIDTH = 768;
 size_t FRAME_HEIGHT = 512;
 u32 frame_buffer[393216];
 
-int wid;
+int wid;  // Window ID.
 
 
 void
 draw_char(u8 ch, u64 dest_x, u64 dest_y)
 {
-	u32* dest = frame_buffer + FRAME_WIDTH * dest_y + dest_x;
-	u32* character_data = font_Inconsolata_22_data[ch];
-	for (size_t x = 0; x < font_Inconsolata_22_width; ++x) {
-		for (size_t y = 0; y < font_Inconsolata_22_height; ++y) {
-			u32* pix_ptr = dest + x + FRAME_WIDTH * y;
-			u32 pixel = character_data[x + font_Inconsolata_22_width * y];
-			u8 alpha = pixel >> 24;
-			if (!alpha) {  // no alpha
-				continue;
-			}
-			if (0xFF == alpha) {
-				*pix_ptr = pixel;
-				continue;
-			}
-			u32 dest_pixel = *pix_ptr;
-			u8 unalpha = 0xFF - alpha;
-			u8 red = (((dest_pixel >> 16) & 255) * unalpha + ((pixel >> 16) & 255) * alpha) / 0xff;
-			u8 green = (((dest_pixel >> 8) & 255) * unalpha + ((pixel >> 8) & 255) * alpha) / 0xff;
-			u8 blue = ((dest_pixel & 255) * unalpha + (pixel & 255) * alpha) / 0xff;
-			*pix_ptr = (alpha << 24) | (red << 16) | (green << 8) | blue;
-		}
+	// Check the inputs.
+	// Trust that the type "u-" means we don't have to check lower bounds?
+	if (ch > font_Inconsolata_22_number_of_characters) {
+		// No error message or anything, just decline to draw.
+		return;
 	}
+	if (dest_x >= (FRAME_WIDTH - font_Inconsolata_22_width)) {
+		return;
+	}
+	if (dest_y >= (FRAME_HEIGHT - font_Inconsolata_22_height)) {
+		return;
+	}
+	carefree_alpha_blend_blit(
+		frame_buffer,
+		font_Inconsolata_22_data[ch],
+		FRAME_WIDTH,
+		dest_x,
+		dest_y,
+		font_Inconsolata_22_width,
+		font_Inconsolata_22_height
+	);
 }
 
 
@@ -49,7 +49,7 @@ draw_char(u8 ch, u64 dest_x, u64 dest_y)
 
 
 void
-mousemove(u64 window_id, u64 new_x, u64 new_y)
+mousedown(u64 window_id, u64 new_x, u64 new_y)
 {
 	u32* pix_ptr = frame_buffer + FRAME_WIDTH * new_y + new_x;
 	*pix_ptr = GREEN;
@@ -61,9 +61,9 @@ void
 main()
 {
 	init_font_data();
-	wid = window_create(FRAME_WIDTH, FRAME_HEIGHT, "Bouncing Ball Example", 0);
+	wid = window_create(FRAME_WIDTH, FRAME_HEIGHT, "Xerblin", 0);
 	draw_background(frame_buffer, FRAME_WIDTH, FRAME_HEIGHT);
-	for (size_t ch = 0; ch < 94; ++ch) {
+	for (size_t ch = 0; ch < font_Inconsolata_22_number_of_characters; ++ch) {
 		draw_char(
 			ch,
 			128 + (ch % 26) * font_Inconsolata_22_width,
@@ -72,6 +72,6 @@ main()
 	}
 	window_draw_frame(wid, frame_buffer);
 	//window_on_keydown(wid, keydown);
-	window_on_mousemove(wid, mousemove);
+	window_on_mousedown(wid, mousedown);
 	enable_event_loop();
 }