diff --git a/.forgejo/run-examples/action.yaml b/.forgejo/run-examples/action.yaml
deleted file mode 100644
index 815e936..0000000
--- a/.forgejo/run-examples/action.yaml
+++ /dev/null
@@ -1,12 +0,0 @@
-# run all Cargo examples, as described here:
-#
-#   Karol Kuczmarski. "Add examples to your Rust libraries"
-#   http://xion.io/post/code/rust-examples.html
-#
-runs:
-  using: "composite"
-  steps:
-    - run: cd app-proto; cargo run --example irisawa-hexlet
-    - run: cd app-proto; cargo run --example three-spheres
-    - run: cd app-proto; cargo run --example point-on-sphere
-    - run: cd app-proto; cargo run --example kaleidocycle
\ No newline at end of file
diff --git a/.forgejo/setup-rust/action.yaml b/.forgejo/setup-rust/action.yaml
deleted file mode 100644
index 6960dc4..0000000
--- a/.forgejo/setup-rust/action.yaml
+++ /dev/null
@@ -1,10 +0,0 @@
-# set up the Rust toolchain. based on David Tolnay's more general
-# `rust-toolchain` action for GitHub
-#
-#   https://github.com/dtolnay/rust-toolchain
-#
-runs:
-  using: "composite"
-  steps:
-    - run: curl --proto '=https' --tlsv1.2 --retry 10 --retry-connrefused --location --silent --show-error --fail 'https://sh.rustup.rs' | sh -s -- -y --profile minimal
-    - run: echo $HOME/.cargo/bin >> $GITHUB_PATH
\ No newline at end of file
diff --git a/.forgejo/workflows/continuous-integration.yaml b/.forgejo/workflows/continuous-integration.yaml
index f821b1d..d200b53 100644
--- a/.forgejo/workflows/continuous-integration.yaml
+++ b/.forgejo/workflows/continuous-integration.yaml
@@ -3,23 +3,46 @@ on:
   push:
     branches: [main]
 jobs:
+  # build the application, reporting success if the build completes
   build:
     runs-on: docker
+    container:
+      image: dyna3:ci
+    defaults:
+      run:
+        working-directory: app-proto
     steps:
       - uses: https://code.forgejo.org/actions/checkout@v4
-      - uses: ./.forgejo/setup-rust
-      - run: rustup target add wasm32-unknown-unknown
-      - run: cargo install trunk
-      - run: cd app-proto; trunk build
+      - run: trunk build
+  
+  # run the automated tests, reporting success if the tests pass
   test:
     runs-on: docker
+    container:
+      image: dyna3:ci
+    defaults:
+      run:
+        working-directory: app-proto
     steps:
       - uses: https://code.forgejo.org/actions/checkout@v4
-      - uses: ./.forgejo/setup-rust
-      - run: cd app-proto; cargo test
+      - run: cargo test
+  
+  # run the Cargo examples, as described here:
+  #
+  #   Karol Kuczmarski. "Add examples to your Rust libraries"
+  #   http://xion.io/post/code/rust-examples.html
+  #
+  # report success if the examples build and run without errors
   run-examples:
     runs-on: docker
+    container:
+      image: dyna3:ci
+    defaults:
+      run:
+        working-directory: app-proto
     steps:
       - uses: https://code.forgejo.org/actions/checkout@v4
-      - uses: ./.forgejo/setup-rust
-      - uses: ./.forgejo/run-examples
\ No newline at end of file
+      - run: cargo run --example irisawa-hexlet
+      - run: cargo run --example three-spheres
+      - run: cargo run --example point-on-sphere
+      - run: cargo run --example kaleidocycle
\ No newline at end of file
diff --git a/tools/ci-image/Dockerfile b/tools/ci-image/Dockerfile
new file mode 100644
index 0000000..de4668e
--- /dev/null
+++ b/tools/ci-image/Dockerfile
@@ -0,0 +1,4 @@
+FROM rust:1.85-slim-bookworm
+RUN rustup target add wasm32-unknown-unknown
+RUN cargo install trunk
+WORKDIR /home
\ No newline at end of file
diff --git a/tools/ci-image/build b/tools/ci-image/build
new file mode 100755
index 0000000..d1a90dc
--- /dev/null
+++ b/tools/ci-image/build
@@ -0,0 +1,5 @@
+#!/bin/sh
+
+# build and tag the Docker image we use for continuous integration
+
+docker build . --tag dyna3:ci
\ No newline at end of file