diff --git a/week13/Gearbox.java b/week13/Gearbox.java
index 45a2fcb..ffe92b2 100644
--- a/week13/Gearbox.java
+++ b/week13/Gearbox.java
@@ -3,15 +3,20 @@ package week13;
 public class Gearbox {
   private int gear = 1;
 
-  public static class IllegalGearChangeException extends RuntimeException {}
+  public static class IllegalGearChangeException extends RuntimeException {
+  }
 
   void changeGear(int newGear) {
-    if(newGear == gear) return;
-    if(newGear != -1 && (newGear < 1 || newGear > 5)) throw new IllegalArgumentException();
+    if (newGear == gear)
+      return;
+    if (newGear != -1 && (newGear < 1 || newGear > 5))
+      throw new IllegalArgumentException();
     // newGear is now either -1 or 1..=5
     var gearToCheck = newGear;
-    if(gearToCheck == -1) gearToCheck++;
-    if(Math.abs(gear - newGear) != 1) throw new IllegalGearChangeException();
+    if (gearToCheck == -1)
+      gearToCheck++;
+    if (Math.abs(gear - gearToCheck) != 1)
+      throw new IllegalGearChangeException();
     gear = newGear;
   }
 }
diff --git a/week13/Printer.java b/week13/Printer.java
index cd51724..77e8db4 100644
--- a/week13/Printer.java
+++ b/week13/Printer.java
@@ -3,51 +3,56 @@ package week13;
 import common.StdRandom;
 
 public class Printer {
-    static class OutOfPaperException extends Exception {
-        @Override
-        public String getMessage() {
-            return "No Paper pack found in printer.\n" +
-            "Check that there's enough paper left for this print job, that the Paper pack is clean and that the paper pack chip is undamaged. "+
-            "Please note that third-party Paper packs may not be supported. Check that the Paper pack is made for this model.";
-        }
-    }
-    static class OutOfTonerException extends Exception {
-        @Override
-        public String getMessage() {
-            return "Printing supply pack is empty or was not found.\n" +
-            "Check that an official Printing supply pack is correctly inserted in the printer, try re-seating if necessary. " +
-            "Check that Printing supply packs are inserted into the correct color coded slots. Check that your Printing resupply subscription is active. " +
-            "Please note that third-party Printing supply packs may not be supported. Check that the Paper pack is made for this model.";
-        }
-    }
-    static class PaperJamException extends Exception {
-        @Override
-        public String getMessage() {
-            return "lp0 on fire.";
-        }
+  static class OutOfPaperException extends Exception {
+    @Override
+    public String getMessage() {
+      return "No Paper pack found in printer.\n" +
+          "Check that there's enough paper left for this print job, that the Paper pack is clean and that the paper pack chip is undamaged. "
+          +
+          "Please note that third-party Paper packs may not be supported. Check that the Paper pack is made for this model.";
     }
+  }
 
-    private static Exception getExceptionFromErrorCode(int errorCode) {
-        return switch(errorCode / 10) {
-            case 0 -> new OutOfPaperException();
-            case 1 -> new OutOfTonerException();
-            case 2 -> new PaperJamException();
-            default -> throw new IllegalArgumentException();
-        };
+  static class OutOfTonerException extends Exception {
+    @Override
+    public String getMessage() {
+      return "Printing supply pack is empty or was not found.\n" +
+          "Check that an official Printing supply pack is correctly inserted in the printer, try re-seating if necessary. "
+          +
+          "Check that Printing supply packs are inserted into the correct color coded slots. Check that your Printing resupply subscription is active. "
+          +
+          "Please note that third-party Printing supply packs may not be supported. Check that the Paper pack is made for this model.";
     }
+  }
 
-    public static void print() throws Exception {
-        var rnd = StdRandom.uniformInt(30);
-        var exception = getExceptionFromErrorCode(rnd);
-        throw exception;
+  static class PaperJamException extends Exception {
+    @Override
+    public String getMessage() {
+      return "lp0 on fire.";
     }
+  }
 
-    public static void main(String[] args) {
-        try {
-            print();
-            System.out.println("Printed successfully, thanks for your patronage.");
-        } catch(Exception e) {
-            System.err.println(e.getMessage());
-        }
+  private static Exception getExceptionFromErrorCode(int errorCode) {
+    return switch (errorCode / 10) {
+      case 0 -> new OutOfPaperException();
+      case 1 -> new OutOfTonerException();
+      case 2 -> new PaperJamException();
+      default -> throw new IllegalArgumentException();
+    };
+  }
+
+  public static void print() throws Exception {
+    var rnd = StdRandom.uniformInt(30);
+    var exception = getExceptionFromErrorCode(rnd);
+    throw exception;
+  }
+
+  public static void main(String[] args) {
+    try {
+      print();
+      System.out.println("Printed successfully, thanks for your patronage.");
+    } catch (Exception e) {
+      System.err.println(e.getMessage());
     }
+  }
 }
diff --git a/week13/doc.typ b/week13/doc.typ
index 128c5f1..ee7d485 100644
--- a/week13/doc.typ
+++ b/week13/doc.typ
@@ -9,7 +9,7 @@
 Explain - in your own words - what is an exception?
 
 An object containing information about why a semi-hidden branching happened, usually used for error states. 
-Thrown exceptions bubble up, as if a return was used, until there's a registered exception handler for a given code region, usually by try/catch.
+Thrown exceptions bubble up the call stack, as if a return was used, until there's a registered exception handler for a given code region, usually by try/catch.
 
 == Exercise 13.05