diff --git a/319timer.subx b/319timer.subx
new file mode 100644
index 00000000..a88af39e
--- /dev/null
+++ b/319timer.subx
@@ -0,0 +1,13 @@
+== code
+
+timer-counter:  # -> _/eax: int
+    # . prologue
+    55/push-ebp
+    89/<- %ebp 4/r32/esp
+    #
+    8b/-> *Timer-counter 0/r32/eax
+$timer-counter:end:
+    # . epilogue
+    89/<- %esp 5/r32/ebp
+    5d/pop-to-ebp
+    c3/return
diff --git a/400.mu b/400.mu
index 05a5463f..ab1c6dc0 100644
--- a/400.mu
+++ b/400.mu
@@ -7,6 +7,9 @@ sig set-cursor-position-on-real-screen x: int, y: int
 sig draw-cursor-on-real-screen g: grapheme
 sig color-rgb color: int -> _/ecx: int, _/edx: int, _/ebx: int
 
+# timer
+sig timer-counter -> _/eax: int
+
 # keyboard
 sig read-key kbd: (addr keyboard) -> _/eax: byte
 
diff --git a/boot.subx b/boot.subx
index 2a896a97..6e622a03 100644
--- a/boot.subx
+++ b/boot.subx
@@ -351,23 +351,8 @@ timer-interrupt-handler:
   b0/copy-to-al 0x20/imm8
   e6/write-al-into-port 0x20/imm8
   31/xor %eax 0/r32/eax
-  # ecx = *Timer-current-color
-  8b/-> *Timer-current-color 1/r32/ecx
   # update *Timer-current-color
-  81 0/subop/add *Timer-current-color 0x01010101/imm32
-  # eax = *Video-memory + 0x1200 (a few rows down from top, around middle of screen)
-  8b/-> *Video-memory-addr 0/r32/eax
-  05/add-to-eax 0x1200/imm32
-  89/copy *eax 1/r32/ecx
-  # eax += 0x400
-  05/add-to-eax 0x400/imm32
-  89/copy *eax 1/r32/ecx
-  # eax += 0x400
-  05/add-to-eax 0x400/imm32
-  89/copy *eax 1/r32/ecx
-  # eax += 0x400
-  05/add-to-eax 0x400/imm32
-  89/copy *eax 1/r32/ecx
+  ff 0/subop/increment *Timer-counter
 $timer-interrupt-handler:epilogue:
   # epilogue
   9d/pop-flags
@@ -376,7 +361,7 @@ $timer-interrupt-handler:epilogue:
   cf/return-from-interrupt
 
 == data
-Timer-current-color:
+Timer-counter:
   0/imm32
 
 == code
diff --git a/ex12.mu b/ex12.mu
new file mode 100644
index 00000000..fe97daa9
--- /dev/null
+++ b/ex12.mu
@@ -0,0 +1,28 @@
+# Checking the timer.
+#
+# To build a disk image:
+#   ./translate ex12.mu            # emits code.img
+# To run:
+#   qemu-system-i386 code.img
+# Or:
+#   bochs -f bochsrc               # bochsrc loads code.img
+#
+# Expected output: text with slowly updating colors
+
+fn main screen: (addr screen), keyboard: (addr keyboard), data-disk: (addr disk) {
+  var fg/ecx: int <- copy 0
+  var prev-timer-counter/edx: int <- copy 0
+  {
+    var dummy/eax: int <- draw-text-rightward screen, "hello from baremetal Mu!", 0x10/x, 0x400/xmax, 0x10/y, fg, 0/bg
+    # wait for timer to bump
+    {
+      var curr-timer-counter/eax: int <- timer-counter
+      compare curr-timer-counter, prev-timer-counter
+      loop-if-=
+      prev-timer-counter <- copy curr-timer-counter
+    }
+    # switch color
+    fg <- increment
+    loop
+  }
+}