Advanced features

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diff --git a/src/content/chapter5_advance_features/lesson03_panic/code.gleam b/src/content/chapter5_advance_features/lesson03_panic/code.gleam
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+++ b/src/content/chapter5_advance_features/lesson03_panic/code.gleam
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+import gleam/io
+
+pub fn main() {
+  print_score(10)
+  print_score(100_000)
+  print_score(-1)
+}
+
+pub fn print_score(score: Int) {
+  case score {
+    score if score > 1000 -> io.println("High score!")
+    score if score > 0 -> io.println("Still working on it")
+    _ -> panic as "Scores should never be negative!"
+  }
+}
diff --git a/src/content/chapter5_advance_features/lesson03_panic/text.html b/src/content/chapter5_advance_features/lesson03_panic/text.html
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+<p>
+  The <code>panic</code> keyword is similar to <code>todo</code> keyword, but it
+  is used to crash the program when the program has reached a point that should
+  never be reached.
+</p>
+<p>
+  This keyword should almost never be used! It may be useful in initial
+  prototypes and scripts, but its use in a library or production application is
+  a sign that the design could be improved. With well designed types the type
+  system can typically be used to make these invalid states unrepresentable.
+</p>