diff --git a/SMILEBASIC/bg.d b/SMILEBASIC/bg.d
new file mode 100644
index 0000000..ea95182
--- /dev/null
+++ b/SMILEBASIC/bg.d
@@ -0,0 +1,110 @@
+module otya.smilebasic.bg;
+import otya.smilebasic.petitcomputer;
+import otya.smilebasic.error;
+import derelict.sdl2.sdl;
+import derelict.opengl3.gl;
+
+struct BGChip
+{
+    int i;
+}
+//912枚まで描画されるみたい
+//->899枚まで描画してその後は一番下のみ描画の様子
+//縦から描画していそう
+class BG
+{
+    BGChip[16384] chip;
+    int offsetx, offsety, offsetz;
+    int clipx, clipy, clipx2, clipy2;
+    int width, height;
+    int rendermax = 899;
+    PetitComputer petitcom;
+    this(PetitComputer pc)
+    {
+        chip[] = BGChip(0);
+        width = 25;
+        height = 35;
+        petitcom = pc;
+    }
+    void render(float disw, float dish)
+    {
+        disw/=2;
+        dish/=2;
+        int z = 0;
+        glColor3f(1.0, 1.0, 1.0);
+        glLoadIdentity();
+        glTranslatef(offsetx / disw, -(offsety / dish), z);
+        //viewport
+        //clipx,clipy
+        glBegin(GL_QUADS);
+        int rendercount = 0;
+        for(int x = 0; x < width; x++)
+        {
+            version(none)
+            {
+                for(int y = 0; y < height; y++){}
+            }
+            for(int y = height - 1; y >= 0; y--)//下から描画してるのか?
+            {
+                BGChip bgc = chip[x + y * width];
+                if(!bgc.i) continue;
+                int u = (bgc.i % 32) * 16;
+                int v = (bgc.i / 32) * 16;
+                int u2 = u + 16;
+                int v2 = v + 16;
+                int w = 16;
+                int h = 16;
+                glTexCoord2f((u) / 512f - 1 , (v2) / 512f - 1);
+                glVertex3f((x * w) / 200f - 1, 1 - (y * h + h) / 120f, 0);
+                glTexCoord2f((u) / 512f - 1, (v) / 512f - 1);
+                glVertex3f((x * w) / 200f - 1, 1 - (y * h) / 120f, 0);
+                glTexCoord2f((u2) / 512f - 1, (v) / 512f - 1);
+                glVertex3f((x * w + w) / 200f - 1, 1 - (y * h) / 120f, 0);
+                glTexCoord2f((u2) / 512f - 1, (v2) / 512f - 1);
+                glVertex3f((x * w + w) / 200f - 1, 1 - (y * h + h) / 120f, 0);
+                rendercount++;
+                if(rendercount >= 899)
+                {
+                    break;
+                }
+            }
+        }
+        glEnd();
+        glLoadIdentity();
+    }
+    void put(int x, int y, int screendata)
+    {
+        int i = screendata & 4095;
+        chip[x + y * width].i = i;
+    }
+    void clear()
+    {
+        chip[0 .. width * height] = BGChip(0);
+    }
+    void screen(int w, int h)
+    {
+        this.width = w;
+        this.height = h;
+        this.clear();
+    }
+    void ofs(int x, int y, int z)
+    {
+        this.offsetx = x;
+        this.offsety = y;
+        this.offsetz = z;
+    }
+    void clip(int x, int y, int x2, int y2)
+    {
+        this.clipx = x;
+        this.clipy = y;
+        this.clipx2 = x2;
+        this.clipy2 = y2;
+    }
+    void clip()
+    {
+        this.clipx = 0;
+        this.clipy = 0;
+        this.clipx2 = 400;
+        this.clipy2 = 240;
+    }
+}