Author: Anders Carlsson <anders.carlsson@sfks.se>
System: Intellivision
Language: IntyBASIC (compiler version 1.4.1 -- June 12, 2019)
Source code: 1011 bytes w/ comments
Executable code: 1593 bytes (ROM format)

How to run:

1. Locate an Intellivision emulator, jzintv recommended
2. On the command line, type: jzintv julgran-inty.rom
3. Program loads and autostarts

How the program works:

First the graphics mode is set up. Since the Intellivsion has a
text resolution of only 20 columns x 12 rows and the Christmas tree
is 23 columns x 14 rows, using text graphics was not an option here.

Thus we cheat a little by enabling the Colored Squares mode, which
is a submode of the Color Stack mode where each position is divided
into four blocky pixels that can have one unique colour each.

A title is displayed at the top, and rest of the screen is prepared
with white pixels.

The input data consists of number of pixels per row and is read one
row at a time. The screen position is calculated based on which row
and how many pixels it contains.

An inner loop then goes through the number of pixels on the row, and
makes adjustments for the case when pixels modulo 4 equals 3, meaning
it should consider what otherwise would be a right column pixel to be
a left column pixel.

Depending on if we're setting a pixel in the upper or lower quadrant,
and left or right quadrant, the required pixel is turned green by a
series of AND and OR statements.

Then the character (containing all four quadrants) is plotted back to
the screen and we WAIT for vertical blank for it to take place.

Finally there is a dummy loop to prevent the program from crashing.

Since this program does not use character graphics, technically it
breaks the challenge rules but as there was no other meaningful way
to do it (possibly using custom characters that are 4x4 pixels each),
this is the best I could come up with.
