Add new GUI themes and update documentation.

- Amber
- LCARS
- Orbital
- Weyland-Yutani
- Kanagawa Paper (dark mode extension)

Update help text to reflect additions.

themes/OldBook.h

@@ -4,10 +4,11 @@
 
 // Expects to be included from GUITheme.h after <imgui.h> and RGBA() helper
 
-static void
-ApplyOldBookTheme()
+// Light variant (existing)
+static inline void
+ApplyOldBookLightTheme()
 {
-	// Sepia old paper aesthetic
+	// Sepia old paper aesthetic (light)
 	const ImVec4 bg0     = RGBA(0xF5E6C8); // paper
 	const ImVec4 bg1     = RGBA(0xEAD9B8);
 	const ImVec4 bg2     = RGBA(0xDECBA6);
@@ -102,4 +103,118 @@ ApplyOldBookTheme()
 	colors[ImGuiCol_PlotLinesHovered]      = blue;
 	colors[ImGuiCol_PlotHistogram]         = yellow;
 	colors[ImGuiCol_PlotHistogramHovered]  = red;
+}
+
+
+// Dark variant (new)
+static inline void
+ApplyOldBookDarkTheme()
+{
+	// Old Book 8 (vim-oldbook8) — exact dark palette mapping
+	// Source: oldbook8.vim (background=dark)
+	const ImVec4 bg0 = RGBA(0x3C4855); // Normal guibg
+	const ImVec4 bg1 = RGBA(0x445160); // Fold/Pmenu bg
+	const ImVec4 bg2 = RGBA(0x626C77); // StatusLine/MatchParen bg
+	const ImVec4 bg3 = RGBA(0x85939B); // Delimiter (used as a lighter hover tier)
+
+	const ImVec4 fg0 = RGBA(0xD5D4D2); // Normal guifg
+	const ImVec4 fg1 = RGBA(0x626C77); // Comment/secondary text
+	const ImVec4 fg2 = RGBA(0xA5A6A4); // Type/Function (used for active controls)
+
+	// Accents from scheme
+	const ImVec4 yellow  = RGBA(0xDDD668); // Search
+	const ImVec4 yellow2 = RGBA(0xD5BC02); // IncSearch
+	const ImVec4 cyan    = RGBA(0x87D7FF); // Visual selection
+	const ImVec4 green   = RGBA(0x5BB899); // DiffAdd
+	const ImVec4 red     = RGBA(0xDB6C6C); // Error/DiffDelete
+
+	ImGuiStyle &style      = ImGui::GetStyle();
+	style.WindowPadding    = ImVec2(8.0f, 8.0f);
+	style.FramePadding     = ImVec2(6.0f, 4.0f);
+	style.CellPadding      = ImVec2(6.0f, 4.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 14.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 4.0f;
+	style.FrameRounding    = 3.0f;
+	style.PopupRounding    = 4.0f;
+	style.GrabRounding     = 3.0f;
+	style.TabRounding      = 4.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 1.0f;
+
+	ImVec4 *colors                = style.Colors;
+	colors[ImGuiCol_Text]         = fg0;
+	colors[ImGuiCol_TextDisabled] = fg1;
+	colors[ImGuiCol_WindowBg]     = bg0;
+	colors[ImGuiCol_ChildBg]      = bg0;
+	colors[ImGuiCol_PopupBg]      = ImVec4(bg1.x, bg1.y, bg1.z, 0.98f);
+	colors[ImGuiCol_Border]       = bg2;
+	colors[ImGuiCol_BorderShadow] = RGBA(0x000000, 0.0f);
+
+	colors[ImGuiCol_FrameBg]        = bg1;
+	colors[ImGuiCol_FrameBgHovered] = bg2;
+	colors[ImGuiCol_FrameBgActive]  = fg2;
+
+	colors[ImGuiCol_TitleBg]          = bg1;
+	colors[ImGuiCol_TitleBgActive]    = bg2;
+	colors[ImGuiCol_TitleBgCollapsed] = bg1;
+
+	colors[ImGuiCol_MenuBarBg]            = bg1;
+	colors[ImGuiCol_ScrollbarBg]          = bg0;
+	colors[ImGuiCol_ScrollbarGrab]        = bg2;
+	colors[ImGuiCol_ScrollbarGrabHovered] = bg3;
+	colors[ImGuiCol_ScrollbarGrabActive]  = fg2;
+
+	colors[ImGuiCol_CheckMark]        = yellow;
+	colors[ImGuiCol_SliderGrab]       = yellow;
+	colors[ImGuiCol_SliderGrabActive] = cyan;
+
+	colors[ImGuiCol_Button]        = bg2;
+	colors[ImGuiCol_ButtonHovered] = bg3;
+	colors[ImGuiCol_ButtonActive]  = fg2;
+
+	colors[ImGuiCol_Header]        = bg2;
+	colors[ImGuiCol_HeaderHovered] = bg3;
+	colors[ImGuiCol_HeaderActive]  = bg3;
+
+	colors[ImGuiCol_Separator]        = bg2;
+	colors[ImGuiCol_SeparatorHovered] = yellow;
+	colors[ImGuiCol_SeparatorActive]  = yellow2;
+
+	colors[ImGuiCol_ResizeGrip]        = ImVec4(fg1.x, fg1.y, fg1.z, 0.12f);
+	colors[ImGuiCol_ResizeGripHovered] = ImVec4(cyan.x, cyan.y, cyan.z, 0.67f);
+	colors[ImGuiCol_ResizeGripActive]  = cyan;
+
+	colors[ImGuiCol_Tab]                = bg1;
+	colors[ImGuiCol_TabHovered]         = bg2;
+	colors[ImGuiCol_TabActive]          = bg2;
+	colors[ImGuiCol_TabUnfocused]       = bg1;
+	colors[ImGuiCol_TabUnfocusedActive] = bg2;
+
+	colors[ImGuiCol_TableHeaderBg]     = bg2;
+	colors[ImGuiCol_TableBorderStrong] = bg1;
+	colors[ImGuiCol_TableBorderLight]  = ImVec4(bg1.x, bg1.y, bg1.z, 0.6f);
+	colors[ImGuiCol_TableRowBg]        = ImVec4(bg1.x, bg1.y, bg1.z, 0.2f);
+	colors[ImGuiCol_TableRowBgAlt]     = ImVec4(bg1.x, bg1.y, bg1.z, 0.35f);
+
+	colors[ImGuiCol_TextSelectedBg]        = ImVec4(cyan.x, cyan.y, cyan.z, 0.28f);
+	colors[ImGuiCol_DragDropTarget]        = yellow;
+	colors[ImGuiCol_NavHighlight]          = yellow;
+	colors[ImGuiCol_NavWindowingHighlight] = ImVec4(fg1.x, fg1.y, fg1.z, 0.70f);
+	colors[ImGuiCol_NavWindowingDimBg]     = ImVec4(0.0f, 0.0f, 0.0f, 0.35f);
+	colors[ImGuiCol_ModalWindowDimBg]      = ImVec4(0.0f, 0.0f, 0.0f, 0.35f);
+	colors[ImGuiCol_PlotLines]             = green;
+	colors[ImGuiCol_PlotLinesHovered]      = cyan;
+	colors[ImGuiCol_PlotHistogram]         = yellow;
+	colors[ImGuiCol_PlotHistogramHovered]  = red;
+}
+
+
+static void
+ApplyOldBookTheme()
+{
+	// Back-compat: keep calling light by default; GUITheme dispatches variants
+	ApplyOldBookLightTheme();
 }