jongalloway · jongalloway · Mar 23, 2026 · Mar 23, 2026
diff --git a/samples/README.md b/samples/README.md
@@ -31,7 +31,7 @@ Dedicated smoke deck for presenter notes packaging, including note-bearing slide
 Speaker-style showcase deck generated from repo content, using `08-showcase.css` plus local Marp SVG assets to cover the Marp ecosystem, MarpToPptx capabilities, presenter notes, and the recommended VS Code task configuration.
 
 9. `09-diagrams.md`
-Diagram-focused sample deck that mixes Mermaid fences and `diagram` fences to exercise DiagramForge-backed flowchart, block, state, mindmap, matrix, pyramid, funnel, and radial output with the companion `09-diagrams.css` theme.
+Diagram-focused sample deck that mixes Mermaid fences and `diagram` fences to exercise DiagramForge-backed flowchart, block, state, mindmap, matrix, and pyramid output with the companion `09-diagrams.css` theme.
 
 ## Theme Decks
 
@@ -52,6 +52,12 @@ Dark-theme smoke deck inspired by the community Dracula theme, using `themes/12-
 5. `themes/13-popular-gaia.md`
 Bright-theme smoke deck inspired by Marp's popular built-in Gaia direction, using `themes/13-popular-gaia.css` to exercise large-scale typography, clean surfaces, and bold section breaks.
 
+6. `themes/14-diagramforge-cyberpunk.md`
+Neon-noir dark theme shared with DiagramForge, using `themes/14-diagramforge-cyberpunk.css` to stress near-black backgrounds, hot-pink/cyan/purple accent hierarchy, and code readability on dark surfaces.
+
+7. `themes/15-diagramforge-synthwave.md`
+Retro-future dark theme shared with DiagramForge, using `themes/15-diagramforge-synthwave.css` to exercise deep-purple backgrounds, sunset-orange/hot-pink accents, and warm dark-stage typography.
+
 ## Running The Samples
 
 Run any sample with the published tool:

diff --git a/samples/themes/14-diagramforge-cyberpunk.css b/samples/themes/14-diagramforge-cyberpunk.css
@@ -0,0 +1,76 @@
+/* @theme diagramforge-cyberpunk */
+
+:root {
+    font-family: "Segoe UI", "Aptos", sans-serif;
+    font-size: 28px;
+    color: #E0E0F0;
+    background-color: #0A0A1A;
+    padding: 44px 58px;
+    line-height: 1.4;
+}
+
+h1 {
+    font-family: "Aptos Display", "Segoe UI", sans-serif;
+    font-size: 58px;
+    color: #FF2D95;
+    font-weight: 700;
+}
+
+h2 {
+    font-size: 40px;
+    color: #00F0FF;
+    font-weight: 700;
+}
+
+h3 {
+    font-size: 30px;
+    color: #8B5CF6;
+    font-weight: 700;
+}
+
+pre,
+code {
+    font-family: "Cascadia Mono", monospace;
+    font-size: 18px;
+    color: #E0E0F0;
+    background: #12122A;
+    line-height: 1.45;
+}
+
+section.lead {
+    background-color: #12122A;
+    color: #E0E0F0;
+}
+
+section.lead h1 {
+    color: #00F0FF;
+}
+
+section.neon {
+    background-color: #0F0F28;
+    color: #E0E0F0;
+}
+
+section.neon h2 {
+    color: #39FF14;
+}
+
+section.accent {
+    background-color: #18082E;
+    color: #E0E0F0;
+}
+
+section.accent h2 {
+    color: #FF2D95;
+}
+
+section.compact {
+    background-color: #0A0A1A;
+    color: #E0E0F0;
+    font-size: 22px;
+}
+
+section.compact h2 {
+    color: #8B5CF6;
+    font-size: 30px;
+}
diff --git a/samples/themes/14-diagramforge-cyberpunk.md b/samples/themes/14-diagramforge-cyberpunk.md
@@ -0,0 +1,71 @@
+---
+theme: diagramforge-cyberpunk
+paginate: true
+lang: en-US
+header: DiagramForge theme smoke
+footer: Cyberpunk sample
+---
+
+<!-- _class: lead -->
+# Cyberpunk Smoke Deck
+
+A neon-noir theme shared with DiagramForge: near-black backgrounds, hot-pink accents, and cyan edge lines.
+
+- Extreme dark stage
+- Neon accent hierarchy
+- Code blocks on surface panels
+- Compact closing slide
+
+---
+
+## Why Cyberpunk?
+
+- Dark backgrounds stress text contrast and glow readability.
+- Multiple neon accents make heading hierarchy failures obvious.
+- Code blocks must stay distinct from the near-black stage.
+
+---
+
+<!-- _class: neon -->
+## Neon Slide
+
+```bash
+marp2pptx slides.md \
+  --theme-css 14-diagramforge-cyberpunk.css \
+  -o slides.pptx
+```
+
+The neon-green heading should contrast sharply with the deep surface while body text stays legible.
+
+---
+
+<!-- _class: accent -->
+## Accent Slide
+
+This slide verifies that the hot-pink accent class applies cleanly to a single slide without bleeding into the next.
+
+Inline `code` should remain readable on the dark surface.
+
+---
+
+## Color Palette
+
+| Role | Color |
+|---|---|
+| Background | `#0A0A1A` |
+| Foreground | `#E0E0F0` |
+| Accent | `#FF2D95` |
+| Surface | `#12122A` |
+| Edge | `#00F0FF` |
+| Group | `#8B5CF6` |
+
+---
+
+<!-- _class: compact -->
+## Close
+
+Final compact slide to confirm the layout stays readable at a smaller font size.
+
+- Theme CSS is loaded.
+- Single-slide class hints are isolated.
+- The rendered PPTX stays editable.
diff --git a/samples/themes/15-diagramforge-synthwave.css b/samples/themes/15-diagramforge-synthwave.css
@@ -0,0 +1,76 @@
+/* @theme diagramforge-synthwave */
+
+:root {
+    font-family: "Segoe UI", "Aptos", sans-serif;
+    font-size: 28px;
+    color: #F0E0FF;
+    background-color: #1A0030;
+    padding: 44px 58px;
+    line-height: 1.4;
+}
+
+h1 {
+    font-family: "Aptos Display", "Segoe UI", sans-serif;
+    font-size: 58px;
+    color: #FF6EC7;
+    font-weight: 700;
+}
+
+h2 {
+    font-size: 40px;
+    color: #FFB347;
+    font-weight: 700;
+}
+
+h3 {
+    font-size: 30px;
+    color: #B24BF3;
+    font-weight: 700;
+}
+
+pre,
+code {
+    font-family: "Cascadia Mono", monospace;
+    font-size: 18px;
+    color: #F0E0FF;
+    background: #2A1040;
+    line-height: 1.45;
+}
+
+section.lead {
+    background-color: #2A1040;
+    color: #F0E0FF;
+}
+
+section.lead h1 {
+    color: #FFB347;
+}
+
+section.sunset {
+    background-color: #220838;
+    color: #F0E0FF;
+}
+
+section.sunset h2 {
+    color: #FF3864;
+}
+
+section.accent {
+    background-color: #2E0A48;
+    color: #F0E0FF;
+}
+
+section.accent h2 {
+    color: #FF6EC7;
+}
+
+section.compact {
+    background-color: #1A0030;
+    color: #F0E0FF;
+    font-size: 22px;
+}
+
+section.compact h2 {
+    color: #B24BF3;
+    font-size: 30px;
+}
diff --git a/samples/themes/15-diagramforge-synthwave.md b/samples/themes/15-diagramforge-synthwave.md
@@ -0,0 +1,71 @@
+---
+theme: diagramforge-synthwave
+paginate: true
+lang: en-US
+header: DiagramForge theme smoke
+footer: Synthwave sample
+---
+
+<!-- _class: lead -->
+# Synthwave Smoke Deck
+
+A retro-future theme shared with DiagramForge: deep purple backgrounds, hot-pink accents, and sunset-orange edge lines.
+
+- Warm dark stage
+- Retro neon palette
+- Code blocks on surface panels
+- Compact closing slide
+
+---
+
+## Why Synthwave?
+
+- Deep-purple backgrounds create a warm dark stage distinct from pure-black themes.
+- Sunset-orange and hot-pink accents stress heading hierarchy readability.
+- Code blocks must remain readable on the violet surface.
+
+---
+
+<!-- _class: sunset -->
+## Sunset Slide
+
+```bash
+marp2pptx slides.md \
+  --theme-css 15-diagramforge-synthwave.css \
+  -o slides.pptx
+```
+
+The neon red-pink heading should pop against the deep surface while body text stays legible.
+
+---
+
+<!-- _class: accent -->
+## Accent Slide
+
+This slide verifies that the hot-pink accent class applies cleanly to a single slide without bleeding into the next.
+
+Inline `code` should remain readable on the deep-purple surface.
+
+---
+
+## Color Palette
+
+| Role | Color |
+|---|---|
+| Background | `#1A0030` |
+| Foreground | `#F0E0FF` |
+| Accent | `#FF6EC7` |
+| Surface | `#2A1040` |
+| Edge | `#FFB347` |
+| Group | `#B24BF3` |
+
+---
+
+<!-- _class: compact -->
+## Close
+
+Final compact slide to confirm the layout stays readable at a smaller font size.
+
+- Theme CSS is loaded.
+- Single-slide class hints are isolated.
+- The rendered PPTX stays editable.
diff --git a/scripts/Invoke-PptxSmokeTest.ps1 b/scripts/Invoke-PptxSmokeTest.ps1
@@ -130,6 +130,16 @@ $repoRoot = Split-Path -Parent $PSScriptRoot
 $generateScript = Join-Path $PSScriptRoot "Generate-LocalPptx.ps1"
 $powerPointScript = Join-Path $PSScriptRoot "Test-PowerPointOpen.ps1"
 $exportSlidesScript = Join-Path $PSScriptRoot "Export-PptxSlides.ps1"
+
+if (-not $ThemeCss) {
+	$resolvedInput = [System.IO.Path]::GetFullPath($InputMarkdown, $repoRoot)
+	$companionCss = [System.IO.Path]::ChangeExtension($resolvedInput, ".css")
+	if (Test-Path $companionCss -PathType Leaf) {
+		$ThemeCss = $companionCss
+		Write-Host "Auto-detected companion theme CSS: $ThemeCss" -ForegroundColor DarkGray
+	}
+}
+
 $usedDefaultOutputPath = $false
 
 if (-not $OutputPath) {