diff --git a/TODO.md b/TODO.md
index be8138f90..94361e92c 100644
--- a/TODO.md
+++ b/TODO.md
@@ -5,13 +5,14 @@ Bugs:
 Performance:
 
 * libuv allocates on every read, we should use a read buffer pool
-* update cells should only update the changed cells
 * for scrollback, investigate using segmented list for sufficiently large
   scrollback scenarios.
 * scrollback: dynamic growth rather than prealloc
 * reflow: text reflow is really poorly implemented right now specifically
   for shrinking columns. Look into this. This may require changing the
   screen data structure.
+* Screen cell structure should be rethought to use some data oriented design,
+  also bring it closer to GPU cells, perhaps.
 
 Correctness:
 
@@ -23,6 +24,7 @@ Correctness:
   - need fallback glyphs if they're not supported
   - can effect a crash using `vttest` menu `3 10` since it tries to parse
     ASCII as UTF-8.
+* Graphemes need to be detected and treated as a single unit
 
 Improvements:
 
diff --git a/src/terminal/Screen.zig b/src/terminal/Screen.zig
index 73466b685..1a8890705 100644
--- a/src/terminal/Screen.zig
+++ b/src/terminal/Screen.zig
@@ -92,9 +92,13 @@ pub const Cell = struct {
     test {
         // We use this test to ensure we always get the right size of the attrs
         const cell: Cell = .{ .char = 0 };
+        _ = @bitCast(u8, cell.attrs);
         try std.testing.expectEqual(1, @sizeOf(@TypeOf(cell.attrs)));
+    }
 
-        log.warn("CELL={}", .{@sizeOf(Cell)});
+    test {
+        //log.warn("CELL={}", .{@sizeOf(Cell)});
+        try std.testing.expectEqual(16, @sizeOf(Cell));
     }
 };
 
diff --git a/src/terminal/color.zig b/src/terminal/color.zig
index 6fa3cc7a8..c8c8a37d4 100644
--- a/src/terminal/color.zig
+++ b/src/terminal/color.zig
@@ -94,10 +94,14 @@ pub const Name = enum(u8) {
 };
 
 /// RGB
-pub const RGB = struct {
+pub const RGB = packed struct {
     r: u8,
     g: u8,
     b: u8,
+
+    test {
+        try std.testing.expectEqual(@as(usize, 3), @sizeOf(RGB));
+    }
 };
 
 test "palette: default" {