The simulator is the default view. It shows one face or both faces of a rule and lets you slide, rotate, zoom, place cursors and read every scale.
The selector on the left of the application bar is both the page title and the model picker:
- 1002 Vector Log-Log Double-Sided Slide Rule - the full-size double-sided rule, 14 scales per face.
- Type 57 Pocket Slide Rule - the single-faced pocket rule.
- Imported rule - appears only after you have imported a rule JSON; it is listed under the name carried by the file. See Import and export.
The count beside the selector is the total number of scales on the model. Switching models resets the slide, the cursors and the displayed face.
- Both faces stacks the two faces on top of each other, each with a small label band. The faces share one slide position, and a cursor line runs through both, so the graduations line up and the readings agree.
- Single shows one face; use Front / Back to choose which.
The Type 57 is single-faced, so Both faces and Back are disabled for it, and the hint line notes that the model has no back.
The middle band is the slide. Press anywhere on it and drag left or right; the cursor changes to a grabbing hand. The slide can travel up to one full scale length in either direction, which is what lets either index reach any value on the body scale. The Reset slide button returns the slide to the aligned position and is disabled while it is already there.
The zoom control sits in the middle of the application bar and runs from 1X to 6X:
- minus and plus step by 0.25.
- The number box is editable; type a ratio and confirm.
- The slider behind it drags continuously.
At 1X the rule fits the viewport width exactly. Above 1X the view scrolls sideways so you can inspect the graduations; zooming keeps the point under the centre of the viewport in place.
Cursors are the vertical lines that cross every scale.
- Add: click an empty part of the face. Up to eight cursors are allowed; further clicks are ignored.
- Move: drag a cursor's handle or line. A click within a few pixels of an existing cursor is treated as a hit and does nothing, so only dragging moves a cursor.
- Remove: use the small ✕ on the cursor's reading card. It appears when the pointer is over the card or when it has keyboard focus. Removing the last cursor leaves the rule with no cursor line; click the face to add one again.
The first cursor uses the theme's cursor colour. Each additional cursor gets a colour from a fixed palette and carries its number on the top handle, matching the number on its reading card.
Rest the pointer on the face without clicking. A dashed guide line follows the pointer, and every scale on the visible face shows a small box with its name and the value under the guide. The read-out covers the whole face, not just the 0-1 span of C/D, so scales whose graduations run past the ends of C/D remain readable. Moving the pointer off the face clears the read-out.
The panel on the right holds one card per cursor, framed in that cursor's colour. Each card lists every scale on the visible face(s) in the order they appear on the rule, and every row sits at the height of the scale it reads. A Front or Back label appears in dual-face mode.
- A reading can be edited. Type a value and press Enter (or move focus away); the cursor moves to the position that reads that value. Input that is out of range or cannot be read on that scale snaps back to the displayed value.
- A movable scale (the slide, or the rotor of a circular rule) gets a second box beside its reading, in the accent colour with a dashed underline. Type a value there and press Enter to move the slide so the scale reads it at the cursor; the cursor stays put. This is the precise way to set the slide: pick a scale that is on the slide, type the value you want it to read, and the slide moves to match. The travel is limited to one scale length, like dragging it.
- Readings that the scale does not define at the cursor's position are shown as a dash and are not editable.
- Movable scales account for the current offset, so a typed value still lands correctly.
- The panel widens with the number of cursors; when there are more cards than fit, the cards scroll sideways.
A circular rule replaces the slide with a rotating rotor:
- Turn the rotor: drag the disc body. The press must travel a few pixels before it counts as a drag, so a click does not nudge the disc.
- Cursors: click the disc to add a radial cursor line at that angle, and drag a line or its round handle to move it. The same colour, numbering and card behaviour as the linear view applies.
- Readings: the panel is headed Readings and each card lists the scales on the visible face. Typing a value turns the cursor to the angle that reads it, taking the rotor offset into account.
- Reset rotation: the button in the readings panel and the reset button in the application bar return the rotor to its printed alignment.
A two-faced circular rule opens dual like a linear one, with the two discs stacked vertically; Single shows one disc and keeps the Front / Back switch available.
The arrows can move the rule without the mouse. It is on by default; switch it off with the left/right-arrow button in the toolbar, beside Import, if it would clash with other shortcuts.
- ← / → move the slide by a small step.
- Shift + ← / → move the last cursor.
While it is on, the footer hint line shows the shortcut. Keystrokes are ignored while a text or number field has focus, so typing is never intercepted.
The Theme button opens a grid of six themes: White Plastic, Vintage Bamboo, High Contrast, Aluminium, Ivory and Engineering Blueprint. A theme restyles both the rule face and the surrounding interface, so the whole page changes together.
The Language selector switches the interface between 简体中文 (zh-CN) and English (en-US). The choice is remembered, and on a first visit the app follows your browser language, using Simplified Chinese only for Chinese locales.
The ? button opens the model-information dialog. It lists the current model's face size, row counts, total scales and single- or double-sided type, then every scale grouped by face and part, with a short description and any printed read-off notes. The dialog also contains the Open quick-start tutorial button, which replays the six-step tour.