broadsheet

A 2D animation engine for algorithm & data-structure explainer videos, in Rust on macroquad. Newspaper-styled, deterministic, code-driven.

Every render looks like a page from the same broadsheet: off-white paper, ink strokes, one spot color, serif headlines, mono data. That's the channel's visual identity — defined once in src/style.rs.

Run the examples

cargo run --example bloom_filter    # live preview window
cargo run --example union_find

Live transport controls (for lining narration up with beats):

The HUD shows exact t and frame number; it is never present in recordings.

Record a video

cargo run --example bloom_filter -- --record out/bloom --fps 60

Renders at a fixed timestep (t = frame / fps, wall clock ignored → output is deterministic), writes out/bloom/frame_00000.png …, then runs ffmpeg if installed — otherwise it prints the exact stitch command:

ffmpeg -framerate 60 -i out/bloom/frame_%05d.png -c:v libx264 -pix_fmt yuv420p bloom.mp4

Recording supersamples at --scale 1.5 by default, so the 1280×720 logical canvas comes out as true 1920×1080 with fonts rasterized at full resolution (pass --scale 2 for 1440p). Everything is drawn with 4× MSAA.

Tip: --fps 2 sparsely samples the whole movie in a few dozen frames — a fast visual proof-read of a full video. --frames N caps the frame count.

Writing a movie

use broadsheet::prelude::*;

fn main() {
    let mut m = Movie::new("Skip Lists", 1280, 720);

    // 1. declare the cast (state at t = 0)
    m.scene()
        .circle("A", v(300., 400.), 40.).label("A")
        .circle("B", v(900., 400.), 40.).label("B").hidden()
        .arrow("e", v(340., 400.), v(340., 400.)).hidden()
        .text("cap", v(640., 620.), "").size(22.).color(FADED).hidden();

    // 2. script the beats (cursor advances with each play)
    m.play(act().set_text("cap", "two nodes, one pointer"));
    m.play(act().fade_in("B").dur(0.4));
    m.play(par![                       // simultaneous
        act().fade_in("e").dur(0.15),
        act().grow_to("e", v(860., 400.)).dur(0.5).ease(InOutCubic),
    ]);
    m.play(seq![                       // sequential
        act().highlight("B", ACCENT),
        act().pulse("B"),
        wait(0.5),                     // narration beat
    ]);
    m.section("Level 2");              // newspaper section card + jump marker
    m.play(act().move_to("A", v(300., 250.)).dur(0.6).ease(OutBack));

    broadsheet::run(m);
}

Verbs: move_to move_by fade_in fade_out color_to highlight (auto-reverts) scale_to pulse shake grow_to/retarget (line & arrow endpoints — draws edges, rewires pointers) set_text (crossfade). Tune any act with .dur(secs) and .ease(...).

Scene niceties: .label("A") puts a mono label riding on a shape (addressable as "A.label"); .follow(id, offset) pins any entity to another; .wrap(px) word-wraps long text (captions) into centred lines; .hidden() starts invisible for a later fade_in; m.wait(s) leaves silence; m.at(t, clip) places a clip at an absolute timestamp; m.now() tells you the cursor time for narration notes.

Palette: INK, PAPER, ACCENT (newsprint red), BLUE, FADED, PAPER_SHADE.

Extending it

See ARCHITECTURE.md — module map, the statelessness invariant, and step-by-step recipes for adding a primitive or a verb (the two things a weekly video occasionally needs).