diff --git a/src/turtle_challenges/cli.py b/src/turtle_challenges/cli.py
index 2173106..cc03102 100644
--- a/src/turtle_challenges/cli.py
+++ b/src/turtle_challenges/cli.py
@@ -10,12 +10,17 @@ from functools import partial
 from turtle_challenges.constants import (
     CHALLENGE_DASHED_LINE,
     CHALLENGE_NAMES,
+    CHALLENGE_RANDOM_WALK,
     CHALLENGE_SHAPES,
+    CHALLENGE_SPIROGRAPH,
     CHALLENGE_SQUARE,
+    SPIROGRAPH_GAP_DEGREES,
 )
 from turtle_challenges.dashed_line import draw_dashed_line
 from turtle_challenges.pen import Pen
+from turtle_challenges.random_walk import random_walk
 from turtle_challenges.shapes import draw_shapes
+from turtle_challenges.spirograph import draw_spirograph
 from turtle_challenges.square import draw_square
 from turtle_challenges.window import (
     TurtleUnavailableError,
@@ -28,7 +33,7 @@ def build_parser() -> argparse.ArgumentParser:
     """!
     @brief Build the argument parser of the command line.
 
-    @return A parser with the challenge name.
+    @return A parser with the challenge name and the spirograph gap option.
     """
     parser = argparse.ArgumentParser(
         prog="turtle-challenges",
@@ -40,14 +45,22 @@ def build_parser() -> argparse.ArgumentParser:
         choices=CHALLENGE_NAMES,
         help="the challenge to run",
     )
+    parser.add_argument(
+        "--gap",
+        type=float,
+        default=SPIROGRAPH_GAP_DEGREES,
+        help="spirograph only: degrees between two circles "
+        f"(default: {SPIROGRAPH_GAP_DEGREES})",
+    )
     return parser
 
 
-def build_challenges(pen: Pen) -> dict[str, Callable[[], None]]:
+def build_challenges(pen: Pen, gap: float) -> dict[str, Callable[[], None]]:
     """!
     @brief Bind every challenge to a turtle.
 
     @param pen The turtle that draws.
+    @param gap Degrees between two circles of the spirograph.
     @return A mapping from the command line name to a function without
         arguments that draws the challenge.
     """
@@ -55,6 +68,8 @@ def build_challenges(pen: Pen) -> dict[str, Callable[[], None]]:
         CHALLENGE_SQUARE: partial(draw_square, pen),
         CHALLENGE_DASHED_LINE: partial(draw_dashed_line, pen),
         CHALLENGE_SHAPES: partial(draw_shapes, pen),
+        CHALLENGE_RANDOM_WALK: partial(random_walk, pen),
+        CHALLENGE_SPIROGRAPH: partial(draw_spirograph, pen, gap),
     }
 
 
@@ -72,6 +87,6 @@ def main(argv: Sequence[str] | None = None) -> int:
         tim = create_pen()
     except TurtleUnavailableError as error:
         parser.exit(1, f"{parser.prog}: error: {error}\n")
-    build_challenges(tim)[args.challenge]()
+    build_challenges(tim, args.gap)[args.challenge]()
     window.exitonclick()
     return 0
diff --git a/src/turtle_challenges/constants.py b/src/turtle_challenges/constants.py
index 0aa941e..feb4956 100644
--- a/src/turtle_challenges/constants.py
+++ b/src/turtle_challenges/constants.py
@@ -92,9 +92,17 @@ CHALLENGE_DASHED_LINE = "dashed-line"
 ## Command line name of challenge 3.
 CHALLENGE_SHAPES = "shapes"
 
+## Command line name of challenge 4.
+CHALLENGE_RANDOM_WALK = "random-walk"
+
+## Command line name of challenge 5.
+CHALLENGE_SPIROGRAPH = "spirograph"
+
 ## Names of the challenges on the command line, in the order of the course.
 CHALLENGE_NAMES: tuple[str, ...] = (
     CHALLENGE_SQUARE,
     CHALLENGE_DASHED_LINE,
     CHALLENGE_SHAPES,
+    CHALLENGE_RANDOM_WALK,
+    CHALLENGE_SPIROGRAPH,
 )
diff --git a/tests/test_cli.py b/tests/test_cli.py
index 7077631..d78b255 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -5,6 +5,7 @@ from turtle_challenges import cli
 from turtle_challenges.constants import (
     CHALLENGE_NAMES,
     DASH_COUNT,
+    SPIROGRAPH_GAP_DEGREES,
     SQUARE_SIDES,
 )
 from turtle_challenges.pen import Pen, Window
@@ -29,7 +30,7 @@ def fake_pen_and_window(monkeypatch: pytest.MonkeyPatch) -> tuple[FakePen, FakeW
 
 
 def test_every_challenge_name_has_a_challenge() -> None:
-    challenges = cli.build_challenges(FakePen())
+    challenges = cli.build_challenges(FakePen(), SPIROGRAPH_GAP_DEGREES)
 
     assert set(challenges) == set(CHALLENGE_NAMES)
 
@@ -39,6 +40,13 @@ def test_parser_accepts_every_challenge_name(name: str) -> None:
     args = cli.build_parser().parse_args([name])
 
     assert args.challenge == name
+    assert args.gap == SPIROGRAPH_GAP_DEGREES
+
+
+def test_parser_reads_the_spirograph_gap() -> None:
+    args = cli.build_parser().parse_args(["spirograph", "--gap", "7.5"])
+
+    assert args.gap == 7.5
 
 
 def test_parser_rejects_an_unknown_challenge(
@@ -82,6 +90,16 @@ def test_main_runs_the_dashed_line(
     assert len(pen.args_of("forward")) == 2 * DASH_COUNT
 
 
+def test_main_passes_the_gap_to_the_spirograph(
+    fake_pen_and_window: tuple[FakePen, FakeWindow],
+) -> None:
+    pen, _ = fake_pen_and_window
+
+    cli.main(["spirograph", "--gap", "90"])
+
+    assert len(pen.args_of("circle")) == 4
+
+
 def test_main_reports_a_missing_turtle_and_exits_with_status_1(
     monkeypatch: pytest.MonkeyPatch, capsys: pytest.CaptureFixture[str]
 ) -> None: