diff --git a/src/render/framebuffer.zig b/src/render/framebuffer.zig
index 2121756..9e38b88 100644
--- a/src/render/framebuffer.zig
+++ b/src/render/framebuffer.zig
@@ -112,6 +112,7 @@ pub const Framebuffer = struct {
     }
 
     /// Draw a filled rectangle
+    /// Optimized with SIMD-friendly @memset for solid colors (alpha=255)
     pub fn fillRect(self: *Self, x: i32, y: i32, w: u32, h: u32, color: Color) void {
         const x_start = @max(0, x);
         const y_start = @max(0, y);
@@ -121,16 +122,28 @@ pub const Framebuffer = struct {
         if (x_start >= x_end or y_start >= y_end) return;
 
         const c = color.toABGR();
+        const row_width = @as(u32, @intCast(x_end - x_start));
+        const ux_start = @as(u32, @intCast(x_start));
 
-        var py = y_start;
-        while (py < y_end) : (py += 1) {
-            const row_start = @as(u32, @intCast(py)) * self.width;
-            var px = x_start;
-            while (px < x_end) : (px += 1) {
-                const idx = row_start + @as(u32, @intCast(px));
-                if (color.a == 255) {
-                    self.pixels[idx] = c;
-                } else if (color.a > 0) {
+        // FAST PATH: Solid colors (alpha=255) use @memset which is SIMD-optimized
+        if (color.a == 255) {
+            var py: u32 = @intCast(y_start);
+            const uy_end: u32 = @intCast(y_end);
+            while (py < uy_end) : (py += 1) {
+                const row_start = py * self.width + ux_start;
+                @memset(self.pixels[row_start..][0..row_width], c);
+            }
+            return;
+        }
+
+        // SLOW PATH: Alpha blending (pixel by pixel)
+        if (color.a > 0) {
+            var py = y_start;
+            while (py < y_end) : (py += 1) {
+                const row_start = @as(u32, @intCast(py)) * self.width;
+                var px = x_start;
+                while (px < x_end) : (px += 1) {
+                    const idx = row_start + @as(u32, @intCast(px));
                     const existing = self.pixels[idx];
                     const bg = Color{
                         .r = @truncate(existing),