diff --git a/.cargo/config.toml b/.cargo/config.toml
new file mode 100644
index 0000000..59431ee
--- /dev/null
+++ b/.cargo/config.toml
@@ -0,0 +1,5 @@
+[alias]
+ coverage = "tarpaulin --out Html --skip-clean"
+
+[build]
+rustc-wrapper = "sccache"
diff --git a/emma/src/chip8/computer.rs b/emma/src/chip8/computer.rs
index 9179faa..53d33ce 100644
--- a/emma/src/chip8/computer.rs
+++ b/emma/src/chip8/computer.rs
@@ -102,9 +102,30 @@ mod test {
     #[test]
     fn decoder_test_invalid_instructions() {
         // 'bad' instructions that should be dropped...
-        //   assert!(matches!(Chip8Computer::decode_instruction(0x5ab1), Chip8CpuInstructions::XXXXERRORINSTRUCTION));
-        //   assert!(matches!(Chip8Computer::decode_instruction(0x8ab8), Chip8CpuInstructions::XXXXERRORINSTRUCTION));
-        //   assert!(matches!(Chip8Computer::decode_instruction(0xeaba), Chip8CpuInstructions::XXXXERRORINSTRUCTION));
+
+        // 5xy0 is the only valid 5 series.
+        assert!(matches!(Chip8CpuInstructions::decode(0x5ab1), Chip8CpuInstructions::XXXXERRORINSTRUCTION));
+        assert!(matches!(Chip8CpuInstructions::decode(0x5abf), Chip8CpuInstructions::XXXXERRORINSTRUCTION));
+
+        // 8__8 -> 8__D and 8__F are invalid
+        assert!(matches!(Chip8CpuInstructions::decode(0x8ab8), Chip8CpuInstructions::XXXXERRORINSTRUCTION));
+        assert!(matches!(Chip8CpuInstructions::decode(0x8abd), Chip8CpuInstructions::XXXXERRORINSTRUCTION));
+        assert!(matches!(Chip8CpuInstructions::decode(0x8abf), Chip8CpuInstructions::XXXXERRORINSTRUCTION));
+
+        // 9__1 -> 9__F are invalid
+        assert!(matches!(Chip8CpuInstructions::decode(0x9ab1), Chip8CpuInstructions::XXXXERRORINSTRUCTION));
+        assert!(matches!(Chip8CpuInstructions::decode(0x9abf), Chip8CpuInstructions::XXXXERRORINSTRUCTION));
+
+        // Only valid E suffixes are 9E and A1
+        assert!(matches!(Chip8CpuInstructions::decode(0xea9d), Chip8CpuInstructions::XXXXERRORINSTRUCTION));
+        assert!(matches!(Chip8CpuInstructions::decode(0xea9f), Chip8CpuInstructions::XXXXERRORINSTRUCTION));
+        assert!(matches!(Chip8CpuInstructions::decode(0xeaa0), Chip8CpuInstructions::XXXXERRORINSTRUCTION));
+        assert!(matches!(Chip8CpuInstructions::decode(0xeaa2), Chip8CpuInstructions::XXXXERRORINSTRUCTION));
+
+        // oh god f is a mess.
+        assert!(matches!(Chip8CpuInstructions::decode(0xf006), Chip8CpuInstructions::XXXXERRORINSTRUCTION));
+        assert!(matches!(Chip8CpuInstructions::decode(0xf008), Chip8CpuInstructions::XXXXERRORINSTRUCTION));
+
     }
 
     #[test]
@@ -120,6 +141,9 @@ mod test {
         let test_computer = Chip8Computer::new_with_program(new_program);
 
         // ...and check the registers
+//        let (high, low) = InstructionUtil::split_bytes(Chip8CpuInstructions::LdVxI(0x10).encode());
+//        assert_eq!(test_computer.memory.peek(0x200), high);
+ //       assert_eq!(test_computer.memory.peek(0x201), low);
     }
 }
 
diff --git a/emma/src/chip8/instructions.rs b/emma/src/chip8/instructions.rs
index 927e168..838708a 100644
--- a/emma/src/chip8/instructions.rs
+++ b/emma/src/chip8/instructions.rs
@@ -1,3 +1,4 @@
+use imgui::ColorPicker3;
 use log::debug;
 use rand::random;
 use crate::chip8::computer::{Chip8Computer};
@@ -213,7 +214,13 @@ impl Chip8CpuInstructions {
             0x5000..=0x5FF0 => {
                 // 5xy0 - SE Vx, Vy
                 // Skip next instruction if Vx = Vy.
-                Chip8CpuInstructions::SeVxVy(x_param, y_param)
+                // if the last nibble isn't 0...
+                if 0xf & input > 0 {
+                    // ... we have a problem.
+                    Chip8CpuInstructions::XXXXERRORINSTRUCTION
+                } else {
+                    Chip8CpuInstructions::SeVxVy(x_param, y_param)
+                }
             }
             0x6000..=0x6FFF => {
                 // 6xkk - LD Vx, byte
@@ -265,13 +272,17 @@ impl Chip8CpuInstructions {
                         Chip8CpuInstructions::ShlVxVy(x_param, y_param)
                     }
                     _ => {
-                        panic!("UNABLE TO DECODE 0x8000 SERIES INSTRUCTION");
+                        Chip8CpuInstructions::XXXXERRORINSTRUCTION
                     }
                 }
             }
             0x9000..=0x9FF0 => {
                 // SNE Vx, Vy
-                Chip8CpuInstructions::SneVxVy(x_param, y_param)
+                if 0xf & input > 0 {
+                    XXXXERRORINSTRUCTION
+                } else {
+                    Chip8CpuInstructions::SneVxVy(x_param, y_param)
+                }
             }
             0xA000..=0xAFFF => {
                 // LD I, Addr