add day 20 of devlog

1 files changed, 10 insertions, 0 deletions

diff --git a/posts/SDL2_devlog.md b/posts/SDL2_devlog.md
index 569fdba..9c4ef41 100644
--- a/posts/SDL2_devlog.md
+++ b/posts/SDL2_devlog.md
@@ -5,6 +5,16 @@ on the editor. The days are listed in reverse chronological
 order, begin from the bottom, if this is your first time on
 this page.
 
+### Day 20
+
+More `lisp` stuff! I added a new brush, for rectangular
+selections. While selection doesn't do much on its own, the
+selected area can be passed onto a `lisp` procedure, for
+example, a procedure to draw horizontal black and white
+lines:
+
+![Day 20](https://u.peppe.rs/frU.mp4)
+
 ### Day 19
 
 Attempted [some isometric