Editor Tour

The window is split into four areas: a top toolbar, the settings sidebar on the left, the live viewport in the middle, and the states/status bar underneath.

Top toolbar

Control	What it does
Lempo menu	App menu (presets, settings, about)
Effect name (Default)	Current effect / preset
2D / 3D toggle	Switch renderer (a purple dot marks the active one)
FOV − / +	3D field of view
Sens − / +	Navigation sensitivity
New / Save / Save As / Open	Effect files use the OS-native file dialog

Sidebar — Emitter panel

The emitter panel is the heart of the effect. Sections top to bottom:

Emitter panel — output, force fields, gravity and emission zone — **Emitter panel** — output, force fields, gravity and emission zone

Section	Key settings
Particle output	`Flow` (particles/sec) · `Max` cap · `Mode` (Infinite / Burst) · `Reverse` · `Align dir.` · `Blend` mode · `Seed`
Force fields v1.2	Turbulence (amount/scale/speed) · Y-axis vortex · attractor (strength/radius/X/Y) · collision plane (Y, bounce, friction) — all off by default
Gravity	Gravity X / Y (world pull on every particle)
Emission zone	Spawn shape (Circle / Rect …), rotation, radius, width, height

Deterministic seed. A nonzero seed makes replay deterministic within each runtime. Python and C++ parity is tested; the browser preview and GDevelop extension have separate spawn implementations, so the same seed does not guarantee identical particle records between them. 0 keeps legacy unseeded behavior.

The Dear PyGui sidebar exposes blend, seed and force-field widgets. The Tk fallback preserves those values on round-trip but has no widgets for them.

States & templates

Under the viewport sits the STATES bar: birth and death chips (plus + to add more). Each state keeps its own color — white means the natural material, any other color tints over the base. Colors cross-fade between states over the particle's life.

The sidebar also carries the templates list — ready-made effects (Explosion, Fire, Rain, Snow in 2D + 3D variants) — and the shape picker:

Shapes & custom assets

12 particle shapes are shared by the 2D and 3D renderers: circle, square, triangle, star, diamond, line, custom, sphere, cube, pyramid, torus, billboard.

Custom shape system — bring your own image or model — **Custom shape system** — bring your own image or model

Custom 3D models & images — upload .glb / .gltf / .obj (or images for 2D). Models render as themselves in the viewport, the browser preview, and in-game. Rigged/skinned GLBs are baked to their rest pose automatically.
Gradual shape morph — birth-to-death shapes cross-fade inside the (0.25, 0.75) window instead of snapping (desktop viewport + browser preview; the game runtime keeps the classic swap for meshes).

Force fields in practice

Field	Behavior
Turbulence	Age-phased noise — subtle drift early, chaos late (or the reverse)
Vortex	Swirl around the Y axis
Attractor	Pull toward a point with linear falloff over the radius
Collision plane	Bounce + friction at a world Y height

All fields are off by default, so legacy motion stays bit-identical when you don't touch them.

Viewport navigation

Mode	Controls (shown at the bottom of the viewport)
2D (GDevelop-style)	`WASD`/arrows move · wheel zooms at cursor · `Space`+drag pans · `F` focus · left-drag gizmo
3D (Blender-style)	`A`/`D` orbit · `W`/`S` dolly · `Q`/`E` up-down · MMB orbit · wheel dolly · `1`/`3`/`7` views · `F` focus

Status area

Particle count & FPS (top-right of the viewport) — e.g. Particles: 20 · FPS: 240 C++ shows the compiled core in use.
STATES chips + Fast preview 60FPS button + a status message (Ready / OK — ready).
Perf HUD — trails mode shows trails: N · verts · draws · sim · render stats.

Above ~900 particles the viewport switches to an adaptive raster path: the particle layer renders offscreen and uploads as a texture while guides and the gizmo stay crisp vector. You get the same look with far fewer draw calls.