1 files changed, 96 insertions, 0 deletions
diff --git a/sample/trick2022/03-mame/remarks.markdown b/sample/trick2022/03-mame/remarks.markdown
new file mode 100644
index 0000000000..c38279f016
--- /dev/null
+++ b/sample/trick2022/03-mame/remarks.markdown
@@ -0,0 +1,96 @@
+Execute the program normally.
+
+```
+$ ruby entry.rb
+```
+
+It shakes a string.
+
+... Wait! This is not all.
+
+Next, please apply "leftward gravity" to each letter in the file.
+IOW, if there is a space to the left of a letter, move it to the left.
+Here, you may want to use the following command.
+
+```
+$ sed "s/ //g" entry.rb | tee up.rb
+```
+
+This program applies "upward gravity" to each letter in an input text.
+The following demo will help you understand what this means.
+
+```
+$ cat test.txt
+$ ruby up.rb test.txt
+```
+
+Now, here's where we come in.
+Please apply "upward gravity" to entry.rb.
+
+```
+$ ruby up.rb entry.rb | tee left.rb
+```
+
+I think that you already noticed that.
+This program applies "leftward gravity" to an input text.
+
+```
+$ cat test.txt
+$ ruby left.rb test.txt
+```
+
+`sed` is no longer required to create `up.rb`; just use `left.rb`.
+
+```
+$ ruby left.rb entry.rb > up.rb
+```
+
+We've come to the final stage.
+Please apply `left.rb` to `left.rb`.
+
+```
+$ ruby left.rb left.rb | tee horizontal.rb
+$ ruby horizontal.rb
+```
+
+Of course, it is also possible to apply `up.rb` to `up.rb`.
+
+```
+$ ruby up.rb up.rb | tee vertical.rb
+$ ruby vertical.rb
+```
+
+Can you tell how they work? Enjoy analyzing!
+
+
+
+---
+Code reading tips (spoiler)
+
+Some code fragments are highly reused between the programs.
+For example, note that this program has one code fragment to input a text
+(`b=$>.read`); `up.rb` and `left.rb` share and use this code fragment.
+Also, `horizontal.rb` and `vertical.rb` share the fragment `puts'TRICK+2022'`.
+Sometimes letters in very distant places are reused all over the place.
+
+Can you tell how it detects if it is already aligned or not yet?
+Here is a simplified version of the gimmick to switch behavior when
+left-aligned:
+
+```
+"\ #{puts('not left-aligned yet')}
+   # {puts('left-aligned')}"
+```
+
+And for top-aligned:
+
+```
+"#
+xx{puts('top-aligned')}
+x#{puts('not top-aligned yet')}
+"
+```
+
+It is also necessary to detect "top-left-aligned" and "left-top-aligned".
+I made tons of subtle adjustments and trial-and-error to create the program.
+I no longer know precisely how it works.