diff --git a/compiler/test/UnitTests.kt b/compiler/test/UnitTests.kt
index 8d7da371e..dc2cc530a 100644
--- a/compiler/test/UnitTests.kt
+++ b/compiler/test/UnitTests.kt
@@ -20,7 +20,7 @@ import prog8.compiler.target.c64.C64MachineDefinition.FLOAT_MAX_NEGATIVE
 import prog8.compiler.target.c64.C64MachineDefinition.FLOAT_MAX_POSITIVE
 import prog8.compiler.target.c64.C64MachineDefinition.Mflpt5
 import prog8.compiler.target.c64.Petscii
-import prog8.compiler.target.cx16.CX16MachineDefinition
+import prog8.compiler.target.cx16.CX16MachineDefinition.CX16Zeropage
 import java.io.CharConversionException
 import java.nio.file.Path
 import kotlin.test.*
@@ -304,11 +304,30 @@ class TestC64Zeropage {
 class TestCx16Zeropage {
     @Test
     fun testReservedLocations() {
-        val zp = CX16MachineDefinition.CX16Zeropage(CompilationOptions(OutputType.RAW, LauncherType.NONE, ZeropageType.BASICSAFE, emptyList(), false, false, Cx16Target))
+        val zp = CX16Zeropage(CompilationOptions(OutputType.RAW, LauncherType.NONE, ZeropageType.BASICSAFE, emptyList(), false, false, Cx16Target))
         assertEquals(zp.SCRATCH_REG, zp.SCRATCH_B1+1, "zp _B1 and _REG must be next to each other to create a word")
     }
 
-    // TODO way more tests for the Cx16 zeropage?
+    @Test
+    fun testFreeSpaces() {
+        val zp1 = CX16Zeropage(CompilationOptions(OutputType.RAW, LauncherType.NONE, ZeropageType.BASICSAFE, emptyList(), true, false, Cx16Target))
+        assertEquals(88, zp1.available())
+        val zp3 = CX16Zeropage(CompilationOptions(OutputType.RAW, LauncherType.NONE, ZeropageType.KERNALSAFE, emptyList(), false, false, Cx16Target))
+        assertEquals(175, zp3.available())
+        val zp4 = CX16Zeropage(CompilationOptions(OutputType.RAW, LauncherType.NONE, ZeropageType.FULL, emptyList(), false, false, Cx16Target))
+        assertEquals(216, zp4.available())
+    }
+
+    @Test
+    fun testReservedSpace() {
+        val zp1 = CX16Zeropage(CompilationOptions(OutputType.RAW, LauncherType.NONE, ZeropageType.FULL, emptyList(), false, false, Cx16Target))
+        assertEquals(216, zp1.available())
+        assertTrue(0x22 in zp1.free)
+        assertTrue(0x80 in zp1.free)
+        assertTrue(0xff in zp1.free)
+        assertFalse(0x02 in zp1.free)
+        assertFalse(0x21 in zp1.free)
+    }
 }
 
 
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index dd744cbf0..c072b5e85 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -11,6 +11,7 @@ TODO
 - optimize several inner loops in gfx2 (highres 4 color mode)
 - use the 65c02 bit clear/set/test instructions for single-bit operations
 - try to fix the bresenham line routines in graphics and gfx2 (sometimes they're a pixel 'off')
+- add modes 2 and 3 to gfx2 (lowres 4 color and 16 color)
 - add a flood fill routine to gfx2?
 - add a f_seek() routine for the Cx16 that uses its seek dos api?
 - optimizer: detect variables that are written but never read - mark those as unused too and remove them, such as uword unused = memory("unused222", 20) - also remove the memory slab allocation
diff --git a/examples/cx16/tehtriz.p8 b/examples/cx16/tehtriz.p8
index 5381d6d19..37a0a1c21 100644
--- a/examples/cx16/tehtriz.p8
+++ b/examples/cx16/tehtriz.p8
@@ -33,7 +33,7 @@ main {
 
 
     sub start() {
-        cx16.screen_set_mode(0)       ; low res
+        void cx16.screen_set_mode(0)       ; low res
         sound.init()
         newGame()
         drawBoard()