Assembly is the mode the Playground opens in. You build with it: place parts, join them by their holes so a screw goes into its hole and a rod passes through its bearing, plug pins into breadboards and headers, and run cables between contacts.

To come back to it from another mode, choose Assembly in the mode box in the top bar.

What is on screen

• Tools, at the top: Select (key Q) picks parts and holes, and Transform (key W) moves and turns them.
• Left: the Outliner (every part in the project), Scene and Environment, and History if it is turned on in App settings.
• Right: Tool Properties (what the tool is doing), Control, Parameters (a part's sizes) and Material.
• Bottom: the Inventory, every part you can add.

Add a part

Click a tile in the Inventory. The part follows the pointer over the floor; click to put it down. Or hover a hole on a part already in the scene to see where the new part would land, and click to put it there, joined. Press Esc, or click the tile again, to put it back.

Join two parts by their holes

1. With the Select tool, hover a part. Its holes show as thin discs.
2. Click a hole on the part you want to move. It is now held, and Tool Properties shows which hole and how big it is.
3. Hover a hole on another part. Where the two can join, a copy of your part is drawn where it would land.
4. Click that hole. Your part jumps into place, and anything fastened to it moves with it.

The move and the joint it makes are one step, so Ctrl+Z takes back both. To let go of a held hole, press Esc or click it again.

Screws, pins and studs are held by their tip. Click a screw's tip, then the hole it goes into. A screw through a plate into a block holds the plate as well.

Turn it afterwards. A part on a hole can still spin about it. After joining, the Transform tool shows one ring and one arrow along the hole, so you can turn the part to where it belongs. ReDo's holes are 10 mm apart, so the right turn is usually a quarter.

Holes and contacts

Hover a part and both its holes and its contacts show: screw holes, studs and axle holes as thin discs, pins, pads and sockets as small squares and posts. Where a hole and a contact sit under the pointer together, the hole wins, so a board's mounting holes stay easy to click among its header pins.

With a contact in hand (a cable, a part with legs, or a pin you clicked) only contacts show, and with a hole in hand only holes.

Plug a part in

1. With the Select tool, hover a part to see its pins, then click a pin to hold it. A pin is held by its tip.
2. Hover a socket that fits, such as a breadboard point or a header. Your part is drawn where it would land.
3. Click. The part plugs in, and Ctrl+Z takes it back out.

A pin needs at least 3 mm of grip in a socket, or must pass right through a hole. A breadboard stays where it is: the part plugged into it comes to it. Press Esc, or click the held pin again, to let go.

A part with pins and no mounting hole, such as a header strip, can go straight from the Inventory onto a socket: click its tile, then the socket.

A board's header rows are bare holes, as a real board is before you solder. Add a Header strip to it first, then plug the header into the breadboard.

Run a cable

1. In the Inventory's Cables category, click a cable to pick it up: the Jumper Cable, Hookup Wire or Connector Cable.
2. Click a contact to start it.
3. Click a second contact to finish it, or click empty space to leave the far end loose.

Press Esc to put the cable down. A Connector Cable starts at a port, such as a JST socket, and ends at another port its plug fits.

• Change a cable afterwards: select it, then set its type and length under Parameters and its colour under Material.
• Move an end: click a placed cable's end to pick it up, then plug it in somewhere else.
• Wire colours: a multi-wire connector cable colours each wire by what its pin carries: black for ground, red for a supply, blue for SDA, yellow for SCL.
• Tidy jumpers: right-click and choose Stick Together to bundle jumpers side by side, or Separate to split them.

Parts with legs

A resistor, an LED and parts like them are placed like a cable: click the part in the Inventory, then click the two holes its legs go into. The part bends its legs to fit the gap. Select it to lift it 5 mm so you can grab a leg and plug it somewhere else.

Warnings

• A cable that joins a supply to ground, such as a battery lead plugged in the wrong way round, is laid but warned of.
• A plug that would land inside another part is refused.
• A cable too short for the gap turns red; click it to let its length grow.
• A plug that does not fit the socket, such as a jumper in a USB port, is refused: each connector fits only its own kind.

ReDo records what is plugged into what, but does not yet simulate the circuit or check it beyond these warnings.

How joined parts move

Each joint lets the parts move as the real ones would. Select a part and Tool Properties lists its joints under Joints:

Drag a joined part with the Transform tool and the gizmo offers only the moves its joints allow. A sliding part stops where the shaft is flush with the end of its hole, or at a shoulder.

• Change how a joint moves from its box under Joints, for example from Turns and slides to Turns only.
• Couple two gears that mesh with Couple under Gears, or right-click and choose Couple Gears.
• Fasten a screw that is already in place: right-click it and choose Fasten.
• Undo a join: right-click a part and choose Detach.
• Ground a part to keep it still while you drag what hangs off it, and Lock to stop an assembly moving at all.

Moving and turning freely

With the Transform tool, Tool Properties holds the move settings:

• Snap to grid moves in steps of 10 mm, the grid every ReDo part sits on.
• Translate step and Rotation step set the steps when snapping is off (0 moves freely). Rotation steps are 15° to start with.
• Check collisions stops a part at the first thing it touches rather than passing through.
• Position and Rotation take typed values.

Press Enter to put the gizmo away and go back to selecting. Every key is on Playground shortcuts.