``` 130 %s=%1-s 140 SPRITE 0,152, %255-a,%s,1 141 PAUSE 3 145 NEXT %a 150 GO TO 106: REM you'll need to stop this with BREAK ``` Execute with **GO TO 100** and you'll see our spaceship fire up its engines and cross the screen from top to bottom. Now for something much fancier as promised, move line **106** to **120** and add these lines: ``` 106 PROC initSXSineMov() 560 STOP 570 DEFPROC initXSineMov() 580 FOR f=0 TO 319:%a[ INT {f}]=% INT {159* SIN (f/159* PI )}: NEXT f 590 ENDPROC ``` Finally modify lines 140 and 150 as follows: ``` 140 SPRITE 0,%159+a[a], %255-a, %s,1 150 GO TO 120 ``` before executing again with **GO TO 100**. The spaceship now will move in a sinusoidal pattern from the bottom to the top of the screen before wrapping around and coming from the bottom. The way we did this, was by precalculating an integer array (See *Chapter 12*) to hold all possible x values within our visible Sprite System coordinates. To avoid **B Integer out of range** errors, we made sure the possible values of both the **SIN** function results and line 140 that positions the spaceship in the *x,y* axis stay within acceptable range. To switch the initial direction of movement, instead of a + you can start with a - in line 140 as follows: ``` 140 SPRITE 0,%159-a[a],%255-a,%s,1 ``` Note that our integer array **%a** is using the brackets **[ ]** variant instead of the parentheses **( )** variant and that's because we have more than a potential **64** values. That means also that integer arrays **%a ()**, **%b ()**, **%c ()**, **%d ()** and **%e ()** have been used up by **%a[ ]**. It's obvious by this example that very complex animation patterns can be created with relative ease using the Sprite System. Before we move on to scrolling, it's useful to also cover a few more subjects we did not address in the course of our example. The first thing is the ability to use palettes with the Sprite System. These are indistinguishable from other palettes in the ZX Spectrum Next palette control system[^p135-2] and they too are also governed by the **PALETTE DIM** keyword to set them up as 8 or 9 bit. Like the **LAYER PALETTE** equivalent, the Sprite System has its own keyword combinations: **SPRITE PALETTE** and **SPRITE PALETTE BANK**. Their syntax is as follows: #### SPRITE PALETTE *n[,i,v]* where *n* is the palette number (**0** for first and **1** for second) while the optional *i, v* are the colour index (**0** to **255**) and colour value (expressed in 9-bit RRRGGGBBB format regardless of the **PALETTE DIM** setting). #### SPRITE PALETTE *n* BANK *b, o* will operate like it's **LAYER** counterpart, assigning palette *n* from offset *o* in bank *b*. As with the **LAYER** version, palettes are 512 bytes long if 9-bit and 256 bytes long if 8-bit (as set with **PALETTE DIM**). [^p135-2]: See Chapter 15 for the Layer 2 notable palette exception