Property reference

Every key Tachyonn understands, with its synonyms, what it maps to and the value
you get when you say nothing. This is the exhaustive list — the
cheat sheet is the short version, and the pages around this
one explain each area in prose.

Kept honest by a test

A test in the repo (tests/docs_reference.rs) reads the parser's source and
fails the build if a key it accepts is missing from this page. If you can write
it in a .tac, it is documented here.

Where each key goes

Scope	Where you write it	What it affects
Project	tac.config in any parent folder	every .tac under it
Theme	a .tt file (or a built-in preset via theme:)	every deck using that theme
Deck	the === … === at the top of the file	that deck
Slide	a === … === right after the ## / #	that slide only

Precedence, weakest to strongest: default.tt → tac.config → theme → deck
frontmatter → per-slide frontmatter. Anything you leave out keeps the value from
the layer before.

Style keys (the second table below) work in all four scopes. Deck keys work
in the first three. Per-slide keys only inside a slide's own block.

A tac.config can also hold macro definitions (<<[<name> …]), and they
cascade the same way — a slide defined once at the top of a course is available
to every deck under it with a plain >>[<name>]. See
the cheatsheet.

Deck keys

Content and structure of the deck itself — not style.

Key (synonyms)	Default	What it does
title	(empty)	Deck title. Feeds the cover and the {title} footer token
subtitle	—	Shown under the title on the cover
author	—	Shown on the cover; {author} footer token
date	—	Metadata only: the {date} footer token
description	—	Metadata only: the {description} footer token. Not cover text — use coverBody:
theme	default	Built-in preset (default, dark, physics) or a path to a .tt file
cover	true	false suppresses the automatically generated cover slide
coverVariant / coverLayout	centered	centered · image-bg · image-title · split · stacked · minimal
coverImage	—	Image or video for the cover (a video plays muted, looping)
coverBody / coverContent	—	Body of the automatic cover. Each occurrence is one line of .tac; repeat the key for more lines (an empty one starts a paragraph)
sectionVariant	centered	centered · toc · toc-side · number · backdrop · color-block · bigtype
tocHeading	section	What sits beside the index on toc-side: section · deck · none
transition	slide	Deck-wide transition family: slide · slide-in · slide-out-in · fade · zoom · none
texMacro / texMacros / macro	—	A global TeX macro (\newcommand{\R}{\mathbb{R}}). Repeat the key to add more
imageMaxWidth / imageMaxSize	1920	Largest side (px) an embedded raster image may have. Also switches on the re-encode of opaque PNGs to JPEG, which is where most of a PDF's weight goes. off embeds every image untouched
imageQuality	82	JPEG quality (1–100) used when an image is re-encoded
css	—	A raw CSS rule. Repeat the key to add more
cssFile / cssFiles	—	Load .css file(s) next to the .tac (comma-separated)
footer.left footer.center footer.right	—	Footer slots: text with {tokens} or an image ![logo.png]

Footer text tokens: {page} {total} {title} {subtitle} {author}
{date} {description}.

Style keys

Each one sets a CSS custom property. Valid in tac.config, in a theme, in the
deck frontmatter and in a single slide's block.

Colors

Key (synonyms)	CSS variable	Default
accent / accentColor	--tac-accent	#FF5F1F
color / textColor	--tac-text	#1c1c28
headingColor / titleColor	--tac-heading	#FF5F1F
mutedColor	--tac-text-muted	#6b7280
borderColor	--tac-border	#e5e7eb
background / bg	(the slide background)	#ffffff
overlay / scrim	--tac-bg-overlay	(none) — dark, light, a number like 0.6, or any CSS color

Typography

Key (synonyms)	CSS variable	Default
font / fontSans	--tac-font-sans	Atkinson Hyperlegible, sans-serif
headingFont / titleFont / fontHeading	--tac-font-heading	Momo Trust Display, sans-serif
fontMono / fontCode	--tac-font-mono	JetBrains Mono, monospace
textSize / fontSize	--tac-text-size	1.8rem
titleSize	--tac-title-size	2.5rem
lineHeight	--tac-line-height	1.8

Spacing & alignment

Key (synonyms)	CSS variable	Default
slidePadding / padding	--tac-slide-padding	4rem 5rem
slidePaddingTop / paddingTop	--tac-slide-padding-top	2.5rem
valign / verticalAlign	--tac-valign	center — accepts top · center · bottom · between · around
reveal / revealMode / clickMode	--tac-reveal-collapse	reserve (1fr) — a hidden >[n]{…} block keeps its space, so the layout never moves between clicks. push (0fr) collapses it instead. See Animations

Cover

Key (synonyms)	CSS variable	Default
coverTitleSize	--tac-cover-title-size	4rem
coverSplitWidth / coverSplit / splitWidth	--tac-cover-split-width	50% — width on split, height on stacked
coverBodySize	--tac-cover-body-size	1.4rem
coverBodyGap	--tac-cover-body-gap	1.6rem

Section dividers

Key (synonyms)	CSS variable	Default
sectionSize	--tac-section-size	3.4rem
sectionBlockColor / sectionBlockBg	--tac-section-block-bg	var(--tac-accent)
sectionBlockTextColor / sectionOnBlock	--tac-section-on-block	#1c1c28
sectionBlockSize	--tac-section-block-size	5rem
sectionBigTypeSize / bigTypeSize	--tac-section-bigtype-size	7rem
kickerSize	--tac-section-kicker-size	1.5rem
kickerColor	--tac-section-kicker-color	var(--tac-text-muted)
kickerFont	--tac-section-kicker-font	(the deck font)

Other layouts

Key (synonyms)	CSS variable	Default
bigNumberSize	--tac-big-number-size	15rem
quoteSize	--tac-quote-size	2.6rem
quoteWidth	--tac-quote-width	70% — width of the quotation box, as a fraction of the slide

Icons (/icon[…])

Key (synonyms)	CSS variable	Default
iconSize	--tac-icon-size	1em — relative to the surrounding text
iconColor	--tac-icon-color	(inherits) — the icon takes the color of wherever it sits

Footer

Key (synonyms)	CSS variable	Default
footerFont	--tac-footer-font	(the deck font)
footerSize / footerTextSize	--tac-footer-size	13px
footerColor	--tac-footer-color	var(--tac-text-muted)

Progress bar

Key (synonyms)	CSS variable	Default
progress / progressBar	--tac-progress-position	bottom — bottom · top · none
progressColor	--tac-progress-color	var(--tac-accent)

Motion

Key (synonyms)	CSS variable	Default
transitionDuration	--tac-trans-dur	0.5s
transitionShift / transitionDistance	--tac-trans-shift	10% — travel of slide-in / slide-out-in
magicDuration / magicMoveDuration	--tac-magic-duration	0.5s

Laser pointer (presenter's mirrored cursor)

Key (synonyms)	CSS variable	Default
laser / laserMode / pointer	--tac-laser-mode	arrow — arrow · dot · ring
laserColor / pointerColor	--tac-laser-color	#FF5F1F
laserTrail / pointerTrail	--tac-laser-trail	off — on leaves a fading trail (dot/ring only)

Utility

Key (synonyms)	Effect
class / classes	Extra CSS classes on the slide root
theme: NAME (as a style key, per slide)	Adds the class theme-NAME
any key starting with --	Passed through verbatim as a CSS custom property

Per-slide keys

Only inside a slide's own === … ===, right after the ## (or #).

Key (synonyms)	Default	What it does
layout	from the heading	Switches the layout (same names as /layout[…])
title	inherited	Overrides the title; none / false / empty removes it
transition	the deck's	Transition into this slide (this is how magic is asked for)
notes	—	Speaker notes for this slide (same as /notes[…])
time / duration	—	Presenter target for this slide: seconds (90) or M:SS / H:MM:SS
footer	from the layout	true / false forces the footer on or off here
footer.left footer.center footer.right	the deck's	Overrides one footer slot on this slide
variant	from the deck	On a cover: its cover variant. On a #: that divider's variant
image / coverImage	—	Cover image for a cover / title slide
kicker / overline / eyebrow	—	Short overline above a # divider's title
toc	true	false keeps this section out of both indexes: the one on the dividers and the T modal

Every style key from the previous section also works here, applied to this slide
alone.

Raw CSS variables

Variables with no friendly key. Set them with their own name (any key starting
with -- passes straight through) in a theme, the deck, or one slide.

Variable	Default	Controls
--tac-title-gap	1.8rem	Space below a slide title
--tac-column-gap	3rem	Gap between columns / image and text
--tac-grid-gap	1.2rem	Gap between grid cards
--tac-section-padding	0 5rem	Section-divider padding
--tac-cover-subtitle-size	2rem	Cover subtitle
--tac-cover-meta-size	1.3rem	Cover author / date
--tac-cover-padding	4rem 6rem	Cover & quote padding
--tac-big-number-label-size	2rem	Big-number label
--tac-quote-cite-size	1.6rem	Quote attribution
--tac-callout-standard	#3b9ad9	### box, standard variant
--tac-callout-alert	var(--tac-accent)	###<alert> box
--tac-callout-example	#2a8a82	###<example> box
--tac-callout-<name>	—	Defines your own ###<name> variant
--tac-bg-dark	#f3f4f6	Shaded surface behind panels
--tac-code-bg	#1e1e1e	Code block background
--tac-footer-height	32px	Footer height
--tac-footer-padding	28px	Footer left/right padding
--tac-progress-height	3px	Progress bar thickness
--tac-cover-overlay	linear-gradient(rgba(0,0,0,.45), rgba(0,0,0,.45))	Scrim over image-bg covers
--tac-cover-on-image	#ffffff	Text color over a cover image
--tac-cover-image-width	60%	Image width on image-title
--tac-cover-image-height	40vh	Image height on image-title
--tac-section-overlay	linear-gradient(rgba(0,0,0,.45), rgba(0,0,0,.45))	Scrim on backdrop dividers
--tac-section-on-image	#ffffff	Text color on backdrop dividers
--tac-section-number-size	6rem	Numeral on number dividers
--tac-section-kicker-gap	0.5em	Space between kicker and title
--tac-section-block-width	78%	Text column width on color-block
--tac-section-block-padding	0 8%	Side padding on color-block
--tac-section-block-rise	6vh	How far above the middle the color-block text sits
--tac-section-bigtype-padding	0 6% 8vh	Padding on bigtype dividers
--tac-toc-active	var(--tac-heading)	Current section in the index
--tac-toc-muted	var(--tac-text-muted)	The other sections
--tac-toc-size	2rem	Index entry size
--tac-toc-gap	0.6em	Vertical gap between entries
--tac-toc-index-display	none	inline-block shows the 1. 2. 3. numbers

Theme-only keys

Valid inside a .tt file (and, where noted, in the frontmatter too).

Key	Default	What it does
name	default	Display name of the theme (informational)
coverLayout / coverVariant	centered	Default cover variant for decks using the theme
sectionVariant	centered	Default section-divider variant
tocHeading	section	Default toc-side heading
texMacro	—	Ships a macro pack with the theme (the deck's own macros win)
footer.<layout>	see below	Whether that layout shows the footer

Footer visibility defaults per layout: title false · section false ·
media false · big-number false · quote true · standard true ·
two-column true · three-column true · grid true · code-window
true · image-and-text true.