v1.4 (6.1.2024)
1. Added cells field flashing when these cells (are about to) appear:
* ASTEROIDS cell (bright colors);
* BEAM/* cells, if their exit from the bottom of the screen would reduce the number of beams shot by the spaceship (bright colors);
* MOTHERSHIP, MUSIC MODE, SKULL (same colors of the cells field when the associated boss/mode is active).
2. Made the spaceship flash red when its shield is low.
3. Made the spaceship glow red for half a second when its shield gets damaged.
4. Made the middle layer appear progressively at the beginning of a game.
5. Made the cells layer populate with empty cells progressively.
6. Changed a few pixels of the title screen spaceship icon and of the Skull.
7. Improved the handling of audio channels.
8. Made sure no sprite tearing occurs when switching between screens.
9. Made sure that the system MMU setup does not interfere.
10. Fixed crash when a tune was started while another tune was playing (e.g. when the MUSIC MODE cell was caught while missiles were active).
11. Fixed the stopping of the music mode music (it inhibited the restart of the spaceship afterburner sound).
12. Fixed the X position of specifically-requested cells (it was equal to the type of the cell removed at the same time).
13. Fixed the lengths of some sounds samples (they were odd).
14. Made various speed and memory optimizations.
15. Made the startup and cleanup code more robust.
16. Worked on the cells:
* improved the handling of the TURN cell (now it is randomized and it ensures that the speeds of the UFOs will always change);
* increased the frequency of the MUSIC MODE cells;
* decoupled the randomization of the cells types and positions;
* created the BOSSES (virtual) class of cells, grouping the BOLTSPITTER and SKULL cells (previously MALUSES) and the MOTHERSHIP cell (previously UNDEFINED) into it;
* made the template of the BOLTSPITTER and SKULL cells striped;
* made the template of the TURN cell fringed;
* made the template of the BEAM/DOUBLE cell equal to that of the other BEAM/* cells.
17. Worked on the audio channels allocation priorities of the sound effects:
* given the Boltspitter bolt shooting and the hitting of the spaceship by the Mothership beam priority over the milestone notification;
* assigned the speech warnings specific priorities (from lowest to highest: "charge low", "shield low", "approaching asteroids", "escapes critical", "danger", "time running out").
18. Updated/improved the documentation.
19. Updated the artwork to reflect the new cells graphics.

v1.3 (23.6.2023)
1. Changed contact email address.

v1.3 (31.7.2022)
1. Improved documentation.

v1.3 (21.5.2022)
1. Added the BEAM/ULTRA cell (shoots a big beam that is equivalent to 5 beams).
2. Moved the lateral beams of the triple beam one pixel down (to match the shape of the ultra beam).
3. Reduced by 16.7% the occurrences of the DAMAGE cell.
4. Worked on the music playback:
* optimized the decoding;
* optimized the handling of the state;
* removed the pairing of channels on the same side (which caused the title and game over screens music to play louder than the in-game music - an originally intended effect which I have changed my mind about - and did not really work for channel 3 as that channel cannot sustain 28836.5 Hz).
5. Slightly improved the standard music quality by re-downsampling the data after improving the amplification.
6. Changed the keyboard handling so that it executes from a level 3 interrupt handler instead of a level 2 interrupt handler, in order to work around issues/lockups caused by expansion hardware sending INT2 interrupt requests.
7. Replaced [SPACE] with [LEFT ALT] and [RIGHT ALT] as [FIRE] button.
8. Made the startup procedure more robust (especially against audio playback performed with direct hardware access by other programs concurrently).
9. Made various little optimizations.
10. Added the possibility of enabling the loading/saving of the hiscore from/to the NVRAM in the Amiga CD³² bootable version - EXPERIMENTAL FEATURE: CHECK OUT THE README ON THE CD FIRST!
11. Worked on cells graphics:
* fixed colors of beams on BEAM/DOUBLE and BEAM/TRIPLE cells;
* fixed a pixel on the border of the ASTEROIDS, BEAM/DOUBLE and BEAM/TRIPLE cells.
12. Worked on manual and stragegy guide:
* renamed DOUBLE BEAM and TRIPLE BEAM as BEAMS/DOUBLE and BEAMS/TRIPLE, respectively;
* added the information for the BEAMS/ULTRA cell;
* adapted the information for the other BEAMS/* cells;
* added the BEAMS paragraph;
* updated the ASTEROIDS, BEAM/DOUBLE and BEAM/TRIPLE cells images;
* updated the CONTROLS table;
* fixed the outer antialiasing of the BEAM/TRIPLE, BOOST and BRAKE cells images;
* fixed the kerning of the last character of the italic strings.
13. Set the default tool of the manual and strategy guide icons to "Apdf".
14. Updated the artwork to reflect the new beams graphics.

v1.2 (11.4.2022)
1. Added the PRESS PLAY ON TAPE edition.
2. Made the BOOST cell increase the scrolling speed by just 50% (instead of 100%).
3. Fixed the chasing of the spaceship (due to a bhi in place of a bhs, downwards missiles would chase the spaceship as a consequence of catching the CHASE cell).
4. Improved the "escapes critical" speech warning.
5. Replaced the title screen writings.
6. Worked on the manual:
* improved/fixed/extended the setup/launch instructions;
* added information relative to the PRESS PLAY ON TAPE edition.
7. Moved history to separate file.
8. Updated/improved installer.
9. Moved 'S' and 'G' one pixel down and inverted pixels at the bottom of 'r' in the small logo in the bonus directory icon for perfect baseline alignment.
10. Added drawer icon where applicable (the real reason is to ensure that the drawers are shown as intended when browsing the CD from Workbench; however, it can be used also as the icon of the drawer the game is installed in - the installer now even asks if the user wants it; this icon had been omitted until now because it is impossible to provide an icon that suits the styles of all the iconsets available for AmigaOS).
11. Improved the icons layout on the CD.

v1.1beta (12.3.2022)
1. Fixed the asteroids activation (they could activate also after a reset of their timer, e.g. when they were postponed and, in the meanwhile, a milestone was reached).
2. Fixed the milestone handling (it replenished the shield and the charge in those extremely rare occasions when the ship had just been destroyed, preventing the game over to execute).
3. Fixed the assignment of points when the MUSIC MODE cell was caught while the Boltspitter was active (25 instead of 5 points were awarded).
4. Fixed the audio decompression routine (due to forgetfulness, 1 byte was not changed in one of the two routines involved; that caused noise during playback, but "luckily" the effects with SkillGrid's own music were not audible; in fact, the bug was discovered when the PRESS PLAY ON TAPE Edition was made; also, due to INTREQ.AUD0 being used for multiple purposes, the very last tiny chunk of one-shot music was not played).
5. Fixed the dynamic selection of audio channels (under some rare circumstances, it could steal a channel from music).
6. Fixed the rendering of the halt sign (it processed 18 lines instead of 6).
7. Fixed a data file (it contained about 3 kB of useless data).
8. Fixed the (potential) malfunctioning caused by hiscore saving when the game booted from CD on an Amiga CD³² configured to have nonvolatile.library save data on a device other than NVRAM (i.e. when there is a volume that has Prefs/Env-Archive/Sys/nv_location defined). See also the notes below about hiscore saving.
9. Fixed/improved/updated the manual (in particular: in one place it erroneously said that the scrolling speed is halved when the Skull activates, which is false; it failed to mention that the TURN cells award 25 points in music mode).
10. Changed the BRAKE cell type from bonus to undefined (as it has a negative effect when time is running out, given that it delays the appearance of cells, and thus also of the TIME cell); graphically, now the cell has a yellow border.
11. Changed the BOOST cell type from malus to undefined (as it has a positive effect when time is running out, given that it accelerates the appearance of cells, and thus also of the TIME cell); graphically, now the cell has a cyan border.
12. Replaced the 30 seconds grace period at the beginning of a game with progressive introduction of the various cells types (this makes for a gentler introduction for beginners and allows to improve/maximize the spaceship power and thus be ready for what will follow).
13. Added the TRIPLE BEAM cell.
14. Changed the look of caught cells so that they appear disabled (instead of flat-filled).
15. Tweaked the transparency of cells when asteroids, Mothership, Skull and music mode are active to preserve their double-color look even if painted in a single color.
16. Fixed one pixel of the POINTS BONUS cell.
17. Made background layer more vivid (but still not obtrusive).
18. Changed flash color when the Boltspitter activates from green ($00ff00) to orange ($ff8000).
19. Improved the sprites:
* modified the palette to make sprites more vibrant and distinguishable;
* added 8 new UFO sprites;
* reworked spaceship, Boltspitter, Morthership and Skull graphics;
* reworked game start, pause and game over writings/icons.
20. Improved the music:
* changed a few volumes for a better mix;
* compressed the bass instrument a little bit;
* increased the S/N ratio by means of the changes above and by reducing some peaks (without causing any distortion);
* lowered by an octave the bass instrument in the "danger" tune;
* improved the compression algorithm for a better compression ratio;
* made the decompression routine faster;
* assigned to the Boltspitter the same tune of the other bosses;
* assigned the "danger" tune (previously assigned to the Boltspitter) to asteroids and missiles.
21. Improved the sound samples:
* removed clicks from a few of them;
* shortened a few of them;
* reworked the explosion sound;
* added the "charge low" speech warning.
22. Added cycling writings (including hiscore) to the title screen.
23. Touched up the graphics of 'M' and 'W' everywhere.
24. Improved the controls:
* replaced [REWIND] with [FIRE2]/[BLUE] so that also a normal 2-button joystick can be used;
* added support for [FIRE2] also to the installable version (which is crucial for running it on Amiga CD³² consoles that do not have a keyboard);
* added keyboard support (i.e. now the cursor keys act as joystick directions and [SPACE] as [FIRE1]).
25. Improved file loading so that, when the game is not running from floppies, the SkillGrid?: assigns and the launcher script are no longer needed.
26. Trashed AmigaOS on the Amiga CD³² to gain the RAM necessary to run the game (which requires more RAM than before, and unfortunately at boot the Amiga CD³² kernel steals quite a lot of RAM); as a consequence:
* removed the possibility of quitting to AmigaOS;
* hiscores are saved exclusively to NVRAM (i.e. Prefs/Env-Archive/Sys/nv_location is ignored);
* implemented direct EEPROM access routines to save the hiscore to NVRAM (still, the NVRAM slot is allocated legally and nothing is touched outside of it; as a positive side effect, saving is now much faster). [This feature is disabled - see the beta release notice.]
27. Improved hiscore saving:
* restricted it to just when a new hiscore is made;
* reduced by 6 bytes the occupation in the Amiga CD³² (tiny) NVRAM.
28. Worked on the CD ISO image:
* minimized buffers (to gain RAM);
* laid out files/directories in a manner that will hopefully make the loading faster on the Amiga CD³²;
* added readme.txt to the root directory;
* added printable package artwork and documentation.
29. Made the startup and cleanup code more robust and more likely to succeed in low CHIP RAM situations.
30. Made various speed and memory optimizations.
31. Adapted the game to 3 floppies (unfortunately, due to the additional data, it cannot fit in 2 floppies anymore).
32. Added a strategy guide.
33. Improved the readme.txt files.
34. Worked on icons:
* added icons to all the user-relevant files/directories;
* redrawn / touched up the icons;
* made all icons 72 pixels tall;
* removed paths from the default tools where appropriate.
35. Updated/improved the installer.
36. Removed the "wd" bits from the files on floppies.
37. Reworked the package artwork.

v1.0 (26.4.2019)
1. First release.