commit df874979ee16ae6e9ec9714a32f190989fd25e1a
Author: de <git.daniele@gmail.com>
Date:   Thu Sep 22 12:44:11 2016 +0200

    initial non productive version

diff --git a/code.asm b/code.asm
new file mode 100644
index 0000000..572e880
--- /dev/null
+++ b/code.asm
@@ -0,0 +1,241 @@
+	section .text
+
+; ----------------------------------------------------------------------
+	call clear_screen
+	xor ax, ax                   ; init ds for lodsb
+	mov ds, ax
+
+	;call initial_animation
+	;xor ax, ax                   ; wait for keyboard
+	;int 0x16
+	;call clear_screen
+
+	call init_screen
+
+	; init seed
+;	mov ah, 2                    ; get time
+;	int 0x1a                     ; ch-h, cl-min, dh-sec
+;	mov ax, cx
+;	mov dl, dh
+;	mul dx
+;	xor dx, ax                   ; result in dx
+
+next_brick:
+	call select_brick            ; returns the selected brick in AL
+	mov dh, 4                    ; start at row 4
+	mov dl, 38                   ; and column 38
+	mov bx, 9                    ; show brick
+	call print_brick
+
+	mov cx, 10
+	call wait_abit
+
+	xor bx, bx                   ; clear brick
+	call print_brick
+	jmp next_brick
+
+	db 0
+
+select_brick:
+	mov ah, 2                    ; get time
+	int 0x1a
+	mov ax, cx
+	mov dl, dh
+	mul dx                       ; result in dx:ax
+	xor dx, ax                   ; result in dx
+	mov ax, word [seed_value + 0x7c00]
+	xor ax, dx
+	mov word [seed_value + 0x7c00], ax
+	xor dx, dx
+	mov bx, 7
+	div bx
+	mov al, dl
+	ret
+
+; TODO below mem optimized
+
+; ======================================================================
+
+clear_screen:
+	mov ax, 3                    ; clear screen
+	int 0x10
+	mov ah, 1                    ; hide cursor
+	mov cx, 0x2607
+	int 0x10
+	ret
+
+; ======================================================================
+
+; AL = number of brick
+; DL = column
+; DH = row
+; BX = 9 -> show brick; 0 -> delete brick (BL = start color for brick)
+; on return AX and DX will not be modified
+print_brick:
+	pusha
+	cmp bx, 0
+	jz print_brick_no_color
+	add bl, al
+	mov bh, bl
+	shl bl, 4
+	or bl, bh
+	xor bh, bh
+print_brick_no_color:
+	xor ah, ah                   ; compute the offset of the brick
+	shl ax, 3                    ; ax = ax * 8
+	mov si, ax
+	add si, bricks + 0x7c00
+
+	; bl = color
+	; ds:si = address of brick
+	; dx = position of brick
+	mov cx, 2
+ccc:
+	push cx
+	lodsb                        ; load next two rows of brick
+	call brick_line              ; print first row
+	inc dh
+	call brick_line              ; print second row
+	inc dh
+	pop cx
+	loop ccc
+
+	popa
+	ret
+
+brick_line:
+	; bh = 0
+	; bl = color
+	; dx = position
+	; al = brick data
+	mov ah, 2                    ; set cursor position
+	int 0x10
+	mov cx, 4
+brick_line_a:
+	pusha
+	and al, 128
+	jz brick_line_d
+	mov ax, 0x0958               ; print brick
+	mov cx, 1
+	int 0x10
+brick_line_d:
+	call cursor_right
+	popa
+	shl al, 1
+	loop brick_line_a
+	ret
+
+; ----------------------------------------------------------------------
+
+cursor_right:
+	pusha
+	mov ah, 3                    ; get cursor position
+	xor bx, bx
+	int 0x10
+	inc dl                       ; increase column
+	mov ah, 2                    ; set new cursor position
+	int 0x10
+	popa
+	ret
+
+; ----------------------------------------------------------------------
+
+init_screen:
+	mov cx, 18                   ; 18 rows
+	mov dh, 3                    ; row 3
+init_screen_a:
+	push cx
+	inc dh                       ; inc row
+	xor bx, bx
+	mov ah, 2                    ; set cursor position
+	mov dl, 33                   ; column
+	int 0x10
+	call init_screen_write_x
+	mov ah, 2                    ; set cursor position
+	mov dl, 46                   ; column
+	int 0x10
+	call init_screen_write_x
+	pop cx
+	loop init_screen_a
+	mov ah, 2                    ; set cursor position
+	mov dl, 33
+	int 0x10
+	mov ax, 0x0958               ; write character
+	mov cx, 13
+	mov bl, 0x77                 ; gray on gray
+	int 0x10
+	ret
+
+init_screen_write_x:
+	mov ax, 0x0958
+	mov cx, 1
+	mov bx, 0x77
+	int 0x10
+	ret
+
+; ----------------------------------------------------------------------
+
+initial_animation:
+	mov ah, 2                    ; set cursor position
+	xor bx, bx
+	mov dh, 5
+	mov dl, 10
+	int 0x10
+	mov si, message + 0x7c00     ; MBR is loaded at address 0000:7C00
+initial_animation_next:
+	cld
+	lodsb
+	cmp al, 0
+	jne initial_animation_do
+	ret
+initial_animation_do:
+	mov bx, 0x0a                 ; write character
+	mov cx, 1
+	mov ah, 9
+	int 0x10
+	call cursor_right
+	mov cx, 2                    ; wait 2x65536 microseconds
+	call wait_abit
+	jmp initial_animation_next
+
+; ----------------------------------------------------------------------
+
+; wait cx:dx microseconds
+wait_abit:
+	pusha
+	xor dx, dx
+	mov ah, 0x86
+	int 0x15
+	popa
+	ret
+
+; ----------------------------------------------------------------------
+
+message:
+	db "Let's play tetris ...", 0
+
+seed_value:
+	dw 0x1234
+
+bricks:
+	db 01000100b, 01000100b, 11110000b, 00000000b
+	db 01000100b, 01000100b, 11110000b, 00000000b
+
+	db 00100010b, 01100000b, 11100010b, 00000000b
+	db 01100100b, 01000000b, 10001110b, 00000000b
+
+	db 01000100b, 01100000b, 00101110b, 00000000b
+	db 01100010b, 00100000b, 11101000b, 00000000b
+
+	db 01100110b, 00000000b, 01100110b, 00000000b
+	db 01100110b, 00000000b, 01100110b, 00000000b
+
+	db 11000110b, 00000000b, 00100110b, 01000000b
+	db 11000110b, 00000000b, 00100110b, 01000000b
+
+	db 01001110b, 00000000b, 01001100b, 01000000b
+	db 11100100b, 00000000b, 10001100b, 10000000b
+
+	db 01101100b, 00000000b, 10001100b, 01000000b
+	db 01101100b, 00000000b, 10001100b, 01000000b
+