diff --git a/assets/basic.js b/assets/basic.js
index d836ace..2371f64 100644
--- a/assets/basic.js
+++ b/assets/basic.js
@@ -905,7 +905,9 @@ if no arg text were given (e.g. "10 NEXT"), args will have zero length
     // print out prompt text
     print("? "); var rh = sys.read().trim();
 
-    if (!isNaN(rh)) rh = rh*1 // if string we got can be cast to number, do it
+    // if string we got can be cast to number, do it
+    // NOTE: empty string will be cast to 0, which corresponds to GW-BASIC
+    if (!isNaN(rh)) rh = rh*1
 
     if (troValue.arrFull !== undefined) { // assign to existing array
         if (isNaN(rh) && !Array.isArray(rh)) throw lang.illegalType(lnum, rh);
diff --git a/src/net/torvald/tsvm/peripheral/GraphicsAdapter.kt b/src/net/torvald/tsvm/peripheral/GraphicsAdapter.kt
index 894875a..e934236 100644
--- a/src/net/torvald/tsvm/peripheral/GraphicsAdapter.kt
+++ b/src/net/torvald/tsvm/peripheral/GraphicsAdapter.kt
@@ -31,10 +31,14 @@ data class AdapterConfig(
     val paletteShader: String = DRAW_SHADER_FRAG
 )
 
+data class SuperGraphicsAddonConfig(
+    val hasSecondBank: Boolean = false
+)
+
 /**
  * NOTE: if TTY size is greater than 80*32, SEGFAULT will occur because text buffer is fixed in size
  */
-open class GraphicsAdapter(val vm: VM, val config: AdapterConfig) :
+open class GraphicsAdapter(val vm: VM, val config: AdapterConfig, val sgr: SuperGraphicsAddonConfig = SuperGraphicsAddonConfig()) :
     GlassTty(config.textRows, config.textCols), PeriBase {
 
     override fun getVM(): VM {
@@ -152,7 +156,7 @@ open class GraphicsAdapter(val vm: VM, val config: AdapterConfig) :
         faketex = Texture(pm)
         pm.dispose()
 
-        // initialise with NONZERO value; value zero corresponds with opaque black, and it will paint the whole screen black
+        // initialise with NONZERO value; value zero corresponds to opaque black, and it will paint the whole screen black
         // when in text mode, and that's undesired behaviour
         // -1 is preferred because it points to the colour CLEAR, and it's constant.
         spriteAndTextArea.fillWith(-1)
diff --git a/terranmon.txt b/terranmon.txt
index 666fbd2..1929501 100644
--- a/terranmon.txt
+++ b/terranmon.txt
@@ -168,17 +168,23 @@ FI
     Palette stored in following pattern: 0b rrrr gggg, 0b bbbb aaaa, ....
     Palette number 255 is always full transparent (bits being all zero)
 
-Optional Sprite Card
-16 bytes
-    Reserved
-65520 bytes:
-    (0th sprite is always the GUI cursor, thus 251 sprites)
-    2 bytes
-        Ob hv000pxy yyyyyyyy (p: 0 for above-text, 1 for below-text, h: horizontal flip, v: vertical flip, x: show/hide, y: y-position)
-    2 bytes
-        0b rr0000xx xxxxxxxx (r: rotation, x: x-position)
+Optional Sprite Card (VRAM Bank 1 (256 kB))
+250880 bytes
+    Secondary framebuffer
+533 bytes: Sprite attribute table
+    (41 sprites total, of which 1 is GUI cursor)
+    12 bytes - signed fixed point
+        X-position
+        Y-position
+        Transform matrix A..D
+    1 bytes
+        0b 0000 00vp
+        (p: 0 for above-all, 1 for below-text, v: show/hide)
+10496 bytes: Sprite table
     256 bytes
         16x16 texture for the sprite
+235 bytes:
+    unused
 
 MMIO