( uxnasm projects/examples/demos/snake.tal bin/snake.rom && uxnemu bin/snake.rom )

%+  { ADD } %-   { SUB }              %/   { DIV }  
%<  { LTH } %>   { GTH }  %=  { EQU } %!   { NEQ } 
%++ { ADD2 } %-- { SUB2 }              %// { DIV2 } 
%<< { LTH2 } %>> { GTH2 } %== { EQU2 } %!! { NEQ2 }  
%2/  { #01 SFT } %2* { #10 SFT }
%8//  { #03 SFT2 } %8**  { #30 SFT2 }
%MOD { DIVk MUL SUB }
%RTN { JMP2r }
%TOS { #00 SWP }
%SWP? { #01 JCN SWP }
%RTN? { #01 JCN RTN }
%BRK? { #01 JCN BRK }

%DIFFICULTY { #06 }

( devices )

|00 @System     [ &vector $2 &wst      $1 &rst    $1 &pad   $4 &r      $2 &g      $2 &b    $2 &debug  $1 &halt $1 ]
|10 @Console    [ &vector $2 &read     $1 &pad    $5 &write $1 &error  $1 ]
|20 @Screen     [ &vector $2 &width    $2 &height $2 &pad   $2 &x      $2 &y      $2 &addr $2 &pixel  $1 &sprite $1 ]
|30 @Audio0     [ &vector $2 &position $2 &output $1 &pad   $3 &adsr   $2 &length $2 &addr $2 &volume $1 &pitch $1 ]
|80 @Controller [ &vector $2 &button   $1 &key    $1 ]
|b0 @DateTime   [ &year   $2 &month    $1 &day    $1 &hour  $1 &minute $1 &second $1 &dotw $1 &doty   $2 &isdst $1 ]

( variables )

|0000

( program )

@arena
	&w $1 &h $1 &timer $1
@apple
	&x $1 &y $1
@snake
	&direction $1 &length $1 &dead $1
	&x $1 &y $1
	&tail

|0100 ( -> )

	( theme ) 
	#0f7e .System/r DEO2 
	#0fe6 .System/g DEO2 
	#0f62 .System/b DEO2

	( vectors )
	;on-frame .Screen/vector DEO2
	;on-button .Controller/vector DEO2

	( resize )
	#00c8 .Screen/width DEO2
	#0100 .Screen/height DEO2

	( set arena )
	.Screen/width DEI2 8// NIP .arena/w STZ
	.Screen/height DEI2 8// NIP .arena/h STZ

	;reset JSR2

BRK

@on-frame ( -> )

	.arena/timer LDZ INC DUP .arena/timer STZ
		DIFFICULTY = BRK?

	( clear ) #00 ;draw-snake JSR2
	( update ) ;move JSR2
	( draw ) #02 .snake/dead LDZ + ;draw-snake JSR2
	( score ) .snake/length LDZ #41 ;draw-score JSR2
	( reset ) #00 .arena/timer STZ

BRK

@on-button ( -> )

	.Controller/button DEI 
	DUP #08 ! ,&no-escape JCN
		;reset JSR2
		&no-escape
	#04 SFT DUP #00 = ,&skip JCN
		DUP .snake/direction STZ
		&skip
	POP

BRK

@reset ( -- )

	#00 ;draw-snake JSR2
	#00 ;draw-apple JSR2

	.arena/w LDZ 2/ #01 - .snake/x STZ
	.arena/h LDZ 2/ #01 - .snake/y STZ
	#00 .snake/dead STZ
	#00 .snake/length STZ
	#00 .snake/direction STZ

	#03 ;draw-snake JSR2
	;add-apple JSR2

RTN

@move ( -- )

	( tail )
	.snake/x LDZ2 STH2
	.snake/length LDZ #00
	&loop
		( pop ) DUP 2* .snake/tail + LDZ2 STH2 SWP2r
		( push ) DUP 2* .snake/tail + STH2r ROT STZ2
		INC GTHk ,&loop JCN
	POP2
	POP2r

	.snake/dead LDZ #00 = RTN?

	.snake/direction LDZ
	DUP #01 ! ,&no-up JCN
		.snake/y LDZ #01 - 
			.arena/h LDZ LTHk SWP? POP 
			.snake/y STZ
		&no-up
	DUP #02 ! ,&no-down JCN
		.snake/y LDZ INC
			.arena/h LDZ MOD
			.snake/y STZ
		&no-down
	DUP #04 ! ,&no-left JCN
		.snake/x LDZ #01 - 
			.arena/w LDZ LTHk SWP? POP 
			.snake/x STZ
		&no-left
	DUP #08 ! ,&no-right JCN
		.snake/x LDZ INC 
			.arena/w LDZ MOD
			.snake/x STZ
		&no-right
	POP

	( detect collision with apple )
	.snake/x LDZ2 .apple/x LDZ2 [ ROT = ROT ROT = #0101 !! ] ,&no-collision-apple JCN
		#00 ;draw-apple JSR2
		.snake/length LDZ INC .snake/length STZ
		;add-apple JSR2
		;move JSR2
		&no-collision-apple

	.snake/length LDZ #01
	&loop-body
		( pop ) DUP 2* .snake/tail + LDZ2 
		.snake/x LDZ2 [ ROT = ROT ROT = #0101 !! ] ,&no-collision-body JCN
			#01 .snake/dead STZ
			#03 ;draw-snake JSR2
			&no-collision-body
		INC GTHk ,&loop-body JCN
	POP2


RTN

@add-apple ( -- )

	.DateTime/hour DEI2 .DateTime/minute DEI2 MUL2 #1234 MUL2 +
		.arena/w LDZ MOD .apple/x STZ
	.DateTime/hour DEI2 .DateTime/minute DEI2 MUL2 #abcd MUL2 +
		.arena/h LDZ MOD .apple/y STZ
	#83 ;draw-apple JSR2

RTN

@draw-snake ( color -- )

	STH
	( draw tail )
	;snake-icns .Screen/addr DEO2
	.snake/length LDZ #00
	&loop
		DUP 2* .snake/tail + LDZ TOS 8** .Screen/x DEO2
		DUP 2* .snake/tail + INC LDZ TOS 8** .Screen/y DEO2
		STHkr .Screen/sprite DEO
		INC GTHk ,&loop JCN
	POP2
	( draw head )
	.snake/x LDZ TOS 8** .Screen/x DEO2
	.snake/y LDZ TOS 8** .Screen/y DEO2
	;snake-icns/face .Screen/addr DEO2
	STHr .Screen/sprite DEO

RTN

@draw-apple ( color -- )

	.apple/x LDZ TOS 8** .Screen/x DEO2
	.apple/y LDZ TOS 8** .Screen/y DEO2
	;apple-chr .Screen/addr DEO2
	.Screen/sprite DEO

RTN

@draw-score ( score color -- )

	STH
	#0010 .Screen/x DEO2
	#0010 .Screen/y DEO2
	DUP #04 SFT TOS 8** ;font-hex ++ .Screen/addr DEO2
	.Screen/x DEI2 #0008 ++ .Screen/x DEO2
		( draw ) STHkr .Screen/sprite DEO
	#0f AND TOS 8** ;font-hex ++ .Screen/addr DEO2
	.Screen/x DEI2 #0008 ++ .Screen/x DEO2
		( draw ) STHr .Screen/sprite DEO

RTN

( assets )

@snake-icns
	7eff ffff ffff ff7e
	&face
		7eff ffdb ffe7 ff7e
@apple-chr
	0000 76ff ffff 7e3c
	1008 0000 0000 0000
@font-hex ( 0-F )
	007c 8282 8282 827c 0030 1010 1010 1010
	007c 8202 7c80 80fe 007c 8202 1c02 827c
	000c 1424 4484 fe04 00fe 8080 7c02 827c
	007c 8280 fc82 827c 007c 8202 1e02 0202
	007c 8282 7c82 827c 007c 8282 7e02 827c
	007c 8202 7e82 827e 00fc 8282 fc82 82fc
	007c 8280 8080 827c 00fc 8282 8282 82fc
	007c 8280 f080 827c 007c 8280 f080 8080