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Terminal — ASCII / Unicode Data Viz

Unicode bar charts, sparklines, and tables for terminal/markdown/chat output. No images needed — the output diffs in git, pastes into README files, and renders in any monospace context.

Part of the muriel skill — see the top-level index for mission, universal rules, and channel map.

Renderer: muriel/chart.py — Python, zero dependencies.

Available primitives

  • bar_chart() — horizontal bars using block characters (█▉▊▋▌▍▎▏) for sub-cell resolution. Supports negative values, comparison bars, markers, custom fill characters.
  • sparkline() — inline single-line trend via ▁▂▃▄▅▆▇█. Drop into prose or table cells.
  • table() — box-drawing-character tables with aligned columns, numeric formatting, optional separators.

Design rules

  • Label every number. Units and context required (the universal rule applies here too — a chart with unlabeled axes is worse than no chart).
  • Monospace is load-bearing. Ensure the output context renders in a monospace font. Markdown code blocks work. Slack works. Most terminal viewers work. HTML <pre> works.
  • Width budgets matter. Target 80 columns or less unless you know the host is wider. Sparklines fit in any column width.
  • Numeric formatting: right-align, consistent decimals, thousand separators for readability.

Shipped examples

  • ClickSense README — bar charts for feature comparison
  • Cartographer README — session activity sparklines and summary tables
  • Research logs — polars DataFrames printed via table() in JSONL entries

Animated effects — when the terminal IS the artifact

Static primitives above cover the common case (numbers in prose, README badges, log summaries). When the terminal output is the artifact — installer ceremonies, demo openings, deploy banners, README captures shown as GIFs — animation is what carries the message, and the substrate is TerminalTextEffects (TTE) (MIT, Python, pip install terminaltexteffects). A library of ~100 named effects (matrix, decrypt, scattered, rain, sweep, vhsTape, …) that take a string and play it into the terminal as a single composed animation. ANSI-escape backend; no curses, no ncurses dependency.

from terminaltexteffects.effects.effect_decrypt import Decrypt
effect = Decrypt("muriel v0.8.0 — the rigorous round-trip")
with effect.terminal_output() as out:
    for frame in effect:
        out.print(frame)

This is the natural cross-pollination point with vocabularies/kinetic-typography.md: the kinetic-typography rules apply (max contrast, strategic motion, no ambient noise, rehearsed emotional vocabulary) but now the runtime is a terminal cell grid instead of pretext / iblipper. Same rules, new substrate.

Capture as MP4 / GIF (for README hero or video channel hand-off) via asciinema record → agg render, or by piping into muriel.capture's terminal-emulator shot when that ships.

Anti-prescription specific to this substrate. Don't animate text that the reader will need to re-read — animation in a static-replay context is decoration. Reserve TTE for moments where the first reveal carries the entire weight (install completion, deploy success, scene-opener captions). Once captured as a GIF for a README, the GIF replays on every page load; if it's still saying something on the third replay, you over-animated.

When to reach for terminal viz vs image

Use terminal viz when: - The output goes into a README, commit message, or log - The reader needs to copy-paste numbers - Width is constrained (<120 columns) - You want zero dependencies and instant iteration

Use image viz (raster / SVG) when: - Aesthetic typography matters - The data has >2 dimensions (color, shape, size encoding) - The output is a paper figure or store asset - Interactivity or animation matters

Anti-patterns

  • Don't use ASCII when Unicode has better glyphs. ━ not -, │ not |, ▁▂▃▄▅▆▇█ for bars.
  • Don't show more than ~15 bars horizontally without a visual break or a scroll region.
  • Don't use color in terminals whose truecolor support you haven't verified — fall back to ANSI 8 or named tokens.