10-liner: Sweeper

This is a little game for the 2023 NOMAM's BASIC 10-liners Contest. This program fits in the EXTREM-256 category, and it was written using FastBasic 4.6 for the 8-bits ATARI XL/XE computers line. Development started on 2023-03-05, and it took 2+5 days. The final version's date is 2023-03-15.

Description

Clean the floor with your broom. Use the hints of surrounding tiles to avoid mines.

Instructions

Development of the game

A couple of years ago, I wrote a FastBasic demo using DLI to enable a customized GRAPHICS 2 text mode with 8 colors and no flickering. Every paired colors could also be combined to create 4 aditional colors. Using this trick, 13 colors including background were available in a 20x12 text mode or tiles. I was thinking about using that trick in my The Children puzzle game like in PitKat for the 2600, but then I had another idea about DLI support that fitted better in that game and didn't use too many source listing space.

Some days ago, I thought that the trick from the demo could be used in a Minesweeper clone, as this game requires 8 numbers matching 8 different colors, 4 tiles (unknown, flag, doubt "?" and mine) matching 4 mixed colors, and the empty space matching the background. I was sure that game logic would be simple to develope, and could fit in the space left by the setting up for the trick (too much listing space for a tenliner). I started to write a prototype over the demo to measure if it was feasible.

During the development, I defined and redefined the charset and the colors many times as I was adding more features. Of course, I run out of space soon and I had to simplify things. But I also got unexpected glitches, being the most important the one that appeared when I turned P/M graphics on. The HBLANK time was partially used by the ANTIC chip's management of P/M, and I got less CPU cycles to manage PF color registers. The solution was to manage only 3 PF registers, so the number of colors for the trick were reduced from 8 to 7, and the number of mixed colors from 4 to 3. It was not that bad, because I could repeat any of the other colors for the 8 and it couldn't be noticed just because the probability of its appearance is almost 0. Also, instead of modifying colors for all 16 scan lines, I had to leave the 16th intact, because it was running when the next interrupt was triggered.

In order to manage multiple difficulty levels, I had to change data management and built a single DATA byte array with a simple loop to proccess it, dropping blocks or bytes directly into fixed memory areas or system registers like the color palette. Also, in that block I stored some indexed tables that are accessed at certain points of the game. With the extra space I got, I could add sound FXs, a timer and, later, an animated Smiley face.

The levels have a similar difficulty than the original Minesweeper from Windows. This is a comparison of both games:

There are differences between PAL and NTSC computers: the color palette is shifted for the same register values, the screen refresh rate is not the same, affecting the speed of jiffies (Hertz), and the aspect ratio changes. As this game was developed for PAL machines, I had to build a NTSC version of it to match the original.

Download and try

Difficulty Level	Sweeper	Minesweeper
1	Name	EASY	Beginner
Size	9x9	9x9
Mines	10	10
Probability	0.12345	0.12345
2	Name	COOL	Intermediate
Size	13x10	16x16
Mines	20	40
Probability	0.15384	0.15625
3	Name	HARD	Expert
Size	19x11	30x16
Mines	40	99
Probability	0.19138	0.20625

Get the SWEEPER.ATR file and set it as drive 1 in a real Atari (or emulator). Turn the computer on and the game should start after the loading completes. A joystick in port 1 is required.

NOTE: This game is for PAL computers. For NTSC computers, the ATR contains a file called SWEENTSC.XEX with minor changes in color palette, timer and Smiley.

The code

	Sweeper (Minesweeper) (c) 2023 Víctor Parada
	$8000-$81FF: Top half of charset $8200-$83FF: Bottom half of charset $8400-$844D: Custom display list $8500-$8607: Secret screen data $8700-$88FF: Screen data
	This game uses 2 blocks of memory for data: screen (visible board) and secret (internal area with hidden mines and hint numbers). Both blocks are paired byte by byte. Board has a visible size of PxQ, while data size goes from 0 to P+1 and 0 to Q+1 respectively, leaving one row and one column free on each side for simplicity in the hint number computation in the internal area. Rows start every 20 bytes matching screen width. This means that the max visible size of the board should be 18x11, but left and right borders of the internal area could be merged (they are never displayed in the visible board), so the effective max size is 19x11. The total data size is 260 bytes for both areas, but top line in screen can be reused to display messages, timer and counter without conflict, and the bottom line is never displayed.
graphics 31	Clears top 8K of RAM, where P/M graphics will be stored
data d() byte="{binary data}", data byte="{binary data}"	Data block 29 bytes: Smileys 60 bytes: Configs 3 level x 10 words 12 bytes: Tile color mappings 44 bytes: 4 pointer bitmaps (11 bytes each) 85+3 bytes: Top half of the charset 0+3 bytes: Fix for splitted DATA in string format 86+3 bytes: Bottom half of the charset 75+3 bytes: Custom Display List 6+3 bytes: Color palette 2+3 bytes: Enable Display List (560) 2+3 bytes: Redirects screen data (88) 1+3 bytes: Sets horizontal position of P3 (Smiley)
dli set in = {color and charset assignment}	Display List Interrupt (DLI) for the board
dim f(12) byte,w(40),g(240),s,t,p,q,p2, q2,m,x,y,z	Arrays: F(): Fonts mapping to bitmaps: 0-8,mine,tile,flag W(): Relative location of each mine in the board (x+y20) G(): Queue for area cleaning Difficulty level configuration: S: Pointer to screen position of the first board cell (minus 21) T: Pointer to memory storing the secret data of the board (minus 21) P: Width of the board Q: Height of the board P2: Horizontal offset of the board in terms of P/M pixels Q2: Vertical offset of the board in terms of P/M pixels M: Number of mines to hide X: Initial horizontal position of the pointer X: Initial vertical position of the pointer Z: Initial relative position of the pointer in the board (x+y20)
mset $8000,$800,0	Clears data area
graphics 18	Graphics mode 2+16 (text 20x12)
pmgraphics 2	Double height P/M graphics
move adr(d)+90,adr(f),12	Sets up tile mapping
e=adr(d)+146 while peek(e) move e+3,dpeek(e+1),peek(e) e=e+3+peek(e) wend	Loads data into memory
c=pmadr(2)	Gets P/M address of the pointer
dli in	Activates DLI
exec _n 0	Defaults to EASY level
do	MAIN LOOP
mset c,256,0	Removes pointer and smiley
poke 708,$28	Restores dynamic text color
exec _q 0	Prints default smiley
repeat	MENU LOOP
v=10	Current tile value
r=p*q-m	Number of required tiles to clean
mset $8500,$300,0	Cleans hidden data and screen
position 6,0 print #6,"{binary data}";	Prints title
exec _m e+1	Displays current difficulty name
mset s+21,p,f(10) move s+21,s+41,q*20-20	Draws the board
repeat until stick(0)=15	Waits for a released stick
sound	Silence...
repeat	Waits for next difficulty selection or confirmation of the current one
a=stick(0)<15	Was joystick moved?
b=strig(0)=0	Was trigger pressed?
if a	If joystick was moved
e=(e+1) mod 3	Selects next difficulty
exec _n e endif	Loads new level configuration
sound 0,72+7ea-62b,10-4b, a8+b2	Beep? Different tones based on action and level
until a+b	Action was taken
exec _a	Disables atract mode
until b	Start?
exec _m 4	Prints WAIT message
n=0 while n<m	Hides mines
b=rand(p)+rand(q)*20+21	Selects a random cell
a=t+b if peek(a)=0	Is that cell in the board empty?
poke a,9	Yes, hide a mine there
w(n)=b	Saves its position to simplify the hint numbers computation and to reveal them after loosing the game
inc n endif wend	Next mine
sound	Turns of the level selection beep
for n=0 to m-1 for j=-20 to 20 step 20 for i=-1 to 1	Computes hint numbers surrounding each mine
a=t+w(n)+j+i b=peek(a)	Picks a cell and its content
if b<9	Is it not a mine?
poke a,b+1 endif next i next j next n	Increase the counter for that cell
exec _m 0	Prints the number of remaining blocks
exec _c 0	Enables standard pointer
timer k=0	Resets timer
repeat	GAME LOOP
exec _q 0	Prints default smiley
a=stick(0)	Gets stick position
if a<15	If the joystick was moved
sound 0,200,10,6	Sound FX
exec _a	Disables attract mode
x=x+(a&8=0)(x<p)-(a&4=0)(x>1) y=y+(a&2=0)(y<q)-(a&1=0)(y>1)	Computes new coordinates within the limits
z=x+y*20 v=peek(s+z)&$f	Gets the selected cell and its current type
exec _c 0	Moves the pointer to the new position
sound	Enough FX
pause 5	Delay to avoid quick move
elif strig(0)=0 and v>9	If the trigger was pressed over a covered cell
exec _q 1	Displays a gessing smiley
exec _a	Disables attract mode
o=0 exec _c 1	Selects the broom as the action pointer
repeat if stick(0)<15	While the trigger is being pressed, check if the joystick was moved
sound 0,9,10,8	Selection sound
o=(o+1) mod 3 exec _c o+1	Next pointer: (0=broom, 1=flag, 2=clear)
sound	Silence...
repeat	Waits for the joystick to be released
exec _t until stick(0)=15 endif	Updates the onscreen timer
exec _t	Updates the onscreen timer
until strig(0)	Repeat until the trigger is released
if o poke s+z,f(12-o)	If the selected action is not to uncover, puts the corresponding tile (moves between flag and clear)
else v=peek(t+z) poke s+z,f(v)	The action is to reveal the cell content, copying it from the hidden area to the screen
if v=9	If a mine was revealed
exec _q 2	Display a sad Smiley
for a = 30 to 150 sound 0,a,8,15-a/10 next a	Plays and explosion FX
else	A hint was revealed
sound 0,9,8,2	Plays a cleaning sound FX
dec r	Decreases the remaining cells counter
if v=0	If the cell was clear, reveal all surrounding hints
h=0 n=0 mset adr(g),480,0	Initializes queue and pointers
g(n)=z	Stores the current cell at the start of the queue
while g(h)	While the queue has pending cells
for i=-1 to 1 for j=-20 to 20 step 20	Checks for unrevealed cells surrounding it
a=g(h)+i+j	Checks surrounding cell's content
if peek(s+a)=f(10) dec r b=peek(t+a) poke s+a,f(b)	If that cell is still unrevealed, copy its content from the hidden board
if b=0 inc n g(n)=a endif endif next j next i	If that cell was empty, add it to the queue
inc h wend else	Updates pointer for next queue item
pause 2 endif	Delay to allow cleaning FX to be listened
exec _m 0	Displays the final number of remaining cells
sound endif endif	Silence
exec _c 0 endif	Recover the pointer shape
exec _t	Updates the onscreen timer
l=v=9	Was a mine revealed?
until r=0 or l	Game is over when there are no more required blocks or a mine was revealed
exec _m 5+l	Prints DONE or FAIL message
for n=0 to m-1 poke s+w(n),f(11-l-l) next n	In case of success, completes missing flags, otherwise reveal position of each mine, replacing all the flags, except those not over a real mine
if l=0	If last cell was not a mine
exec _q 3	Displays a cool smiley
for a=63 to 0 step -1 sound 0,a,10,a mod 8 pause next a endif	Congratulations sound FX
while strig(0)	The game is over. Waits for the trigger to be pressed and then released
poke 708,peek(20)&$3C*4+12 wend repeat until strig(0)	Continuously changes the color of the game over message
exec _a loop	Disables the attract mode
proc _t	Updates the timer
if k<999	If the timer has not reached its limit, update it
pause	Waits for VBLANK to avoid glitches with system timer
k=(time/2)&$7FFF/25	Converts jiffies into seconds
u$="00" u$=+str$(k) u3$=u$[peek(adr(u$))-2]	Converts a decimal number into a 3 digits string
position 16,0 print #6,color(32) u3$ endif endproc	Prints the updated timer
proc _c a mset c,128,0 pmhpos 2,p2+x8+2 move adr(d)+102+a11,c+q2+y*8-1,11 endproc	Updates pointer position and shape
proc _a poke 77,0 endproc	Disables attract mode
proc _m a position 1,0 if a print #6, "EASYCOOLHARDWAITDONEFAIL"[a*4-3,4] else print #6,rtab(5) r endif endproc	Prints message or required blocks
proc _n e	Gets level config
move adr(d)+30+e*20,adr(s),20 endproc	This MOVE sets up 10 integer variables in a single statement, plus the level as an argument
proc _q a move adr(d)+7*a+1,pmadr(3)+15,8 endproc	Updates Smiley

	Move the joystick to select the difficulty level from EASY, COOL and HARD.

	Press the button to start the game. A pointer will appear over the tiles. You will see the number of tiles to clean at the top left and timer showing the seconds at the top right.
	Use the joystick to move around. Press the button to clean a tile. If a number appears, it says how many mines are adjacent to it, horizontally, vertically or diagonally.
	Clean some other tiles to get an idea about where are the mines. Sometimes, you could find a danger-free area that will be cleaned immediatelly by a single click.
	When you are sure that a tile is hiding a mine, press and hold the button until the broom appears, then move the joystick to get a flag, then release the button.

	To remove a misplaced flag, hold the button over it and move the joystick until a tile appears, and then release the button.
	When you clean all the tiles that are not hiding a mine, the game is complete and the timer shows how many second were required. Try to be quick!!! All unflagged tiles will get their flag.
	If you clean a tile that is hidding a mine, this will explode. Then, the location of every mine will be shown. If you misplaced a flag, it will remain in its place.