These commands affect the position and movement of a named sprite.

Move

This is quite a flexible command so will be covered in parts.

Move to a Given Point

move {sprite-name} (to | by) {x} {y} \[in {duration}\]\

Moves the sprite to the given location (to} or to a location relative to the existing location (by). This can happen immediately or over a given duration.

The locations, x and y are integers - they can be negative and can out outside the currently visible area.

The command completes when the movement has been accomplished.

Move in a Given Direction

move {sprite-name} {direction} {distance} \[in {duration}\]

Direction may be one of horizontally, vertically, up, down, left or right, with the distance in pixels. This can happen immediately or over a given duration.

Move at a Given Rate

Instead of giving a duration to the above commands you specify a rate to move at, in pixels per second, e.g.

move {sprite-name} left 100 at 10 pixels per second

Time units default to seconds if not given.

Alternatively, if you want to start a sprite moving without a particular goal then you can just say:

move {sprite-name} at {x} {y}

Where x and y are integers representing pixels per second, either can be zero. An alternative form of the move with exactly the same effect is:

speed {sprite-name} {x} {y}

Accelerate

In addition to setting a movement rate (speed) you can also set the acceleration rate in both dimensions:

accelerate {sprite-name} at {x} {y}

As above, x and y are integers that represent acceleration in pixels per second per second, either can be negative. You can also use the abbreviation accel.

See also the throw command below.

TBD - accelerating for a given duration or to a target speed.

Scroll

If the sprite was created with a view (i.e. a “window” on to the underlying texture then you can use the following command on it:

scroll {sprite-name} by {x} {y} [pixels per second]

scroll {sprite-name} stop

Whilst this does NOT (strictly speaking) move the sprite it does move the _content- of the sprite which can have a similar effect, for example moving clouds across the sky.

If the scrolled window reaches the edge of the underlying texture then it will be repeated as a mirror repeat and hence may appear seemless. If you want to take advantage of this then use tileable textures.

Rotation Action

rotate {sprite-name} (by | to | at) {angle} \[in {duration}\]

Rotates the sprite arounds its centre by, or to the specified angle. The angle is in degrees with zero pointing upwards and the angle increasing clock wise.

The command completes when the rotation is accomplished.

spin {sprite-name} \["clockwise | anticlockwise | counterclockwise\] \[in\] {rate}

spin {sprite-name} stop

Spins the sprite at the given rate, e.g. “in 1 minute”.

This action continues until explicitly stopped.

circle {sprite-name} \[radius\] i\["clockwise | anticlockwise | counterclockwise\] \[in\] {rate}

circle {sprite-name} stop

Moves the sprite with a circular motion around its current position, the sprite can also be moving and the circular motion will be superimposed, however it is important to start the motion first then apply the spin.

This action continues until explicitly stopped.

Throw / Drop

(throw | launch) {sprite-name} [at] {angle} [with force {speed}]

throw {sprite-name} stop

These commands work in conjunction with the directives “gravity” and “ground”. TODO Add link

This will cause the sprite to start moving as if under the influence of gravity. Angle is in degrees, with zero upwards and increasing clockwise. Speed is given in pixels per second in the scene coordinates (and will be scaled to match the display coordinates scheme).

The sprite will travel until one of three conditions is met:

• it goes “out of bounds” (by default, more than twice the display size in any direction)
• it goes below the ground level as specified in the directive above
• It is explicitly stopped

Sprite location is measured at the centre of the sprite, not its bounds.

Drop is a convenience command equivalent to throw something at 180 degrees with zero speed.

Although these commands involve moving sprites I think it makes more sense to have the commands complete immediately.

Jiggle

(jiggle | jitter) {sprite-name} [by] {x} {y} {step} [with chance {percentage}]

(jiggle | jitter) stop

This command makes the sprite move in a random walk around its actual position. It will never go more than x or y pixels in either direction, and each step will be no larger than step pixels. The position is updated 25 times per second and will only happen if a random percentage is less than percentage, default 100%, i.e. jiggling every 25th of a second. A percentage of 50 or even lower looks quite effective.

When the sprite position is used, for example in a variable or moving by a relative amount then the intended position is used, the jigglyness is ignored for these purposes.

The command completes immediately although jiggling will continue until the stop command

Sway / Wave

(sway | wave) {sprite-name} [to] {degrees} [in] {duration} [with chance {percentage}]

(sway | wave) stop

This makes a gradual adjustment to the skew angle, going up to the skew angle in the given time, down to zero then to the negative angle in the given time, and repeats. The difference between them is that sway operates in the x axis and wave operates in the y axis. You can apply both at the same time.

The percentage chance determines whether a movement will be made at each update (currently once every 25th of a second).

The sway and wave are calculated separately from any other skew value applied, and if you skew a relative amount, or use the skew value in a variable any extra amount of sway or wave will be ignored.

The command completes immediately although skewing will continue until the stop command

Future Intentions

To have the ability to change the centre of rotation, e.g.

rotate {sprite-name} to 45 around 50 50