jetpac.nes/src/background.s, branch mainPort to the NES/Famicom of "Jetpac" from Ashby Computers and Graphics Limited.
https://git.mssola.com/nes/jetpac.nes/atom?h=main2026-03-23T23:34:26ZUse the 'nmi_' prefix for NMI-only functions2026-03-23T23:34:26ZMiquel Sabaté Solàmssola@mssola.com2026-03-23T23:34:26Zurn:sha1:b779e7dc3d44f7b9d90aeeee91ed36cf57d65e95
Signed-off-by: Miquel Sabaté Solà <mssola@mssola.com>
Implement the "take off" animation2026-03-23T22:59:26ZMiquel Sabaté Solàmssola@mssola.com2026-03-23T22:59:26Zurn:sha1:0c9b0ad7938e2ba7e994574b4947e25c82440b8c
This is the animation that is done after clearing a stage. Moreover, and
for the first time since I started development, now we can move into the
next level as intended from the game's design.
Signed-off-by: Miquel Sabaté Solà <mssola@mssola.com>
Simplify the random_valid_y_coordinate function2026-02-10T21:45:20ZMiquel Sabaté Solàmssola@mssola.com2026-02-10T21:45:20Zurn:sha1:1b46ddb0486276de0b0691e10277d206a0763300
This function relies on a pre-computed table to get the "random" numbers
from, but most of the times this is used, it needs to be between some
safe boundaries.
Before this commit, this was done inside of the function, correcting the
fetched value to be above or below these limits. But there was a bug on
the below the grounds limit, in which the 'sbc' instruction could
subtract too much from the fetched value and make enemies appear below
the sky.
Now, this is easy to correct, but since we are cheating with a
pre-computed table, I thought it would be vastly easier to just get a
random table with the "proper" values. That is, random but within the
required boundaries already. Plus, it makes the
'random_valid_y_coordinate' function much faster.
This commit adds a ruby script in bin/ which produces a pseudo-random
table when called, making sure all the requirements are met. We have to
make sure to call this script if we ever change the boundaries at some
point.
Signed-off-by: Miquel Sabaté Solà <mssola@mssola.com>
Increase the upper Y limit for sprites2026-02-03T20:49:34ZMiquel Sabaté Solàmssola@mssola.com2026-02-03T20:40:46Zurn:sha1:4ef68e136eb6276cd7dc39426720ce5d7e87d2d4
Some sprites like enemies and objects are meant to appear maximum at a
certain Y coordinate. Increase that as the former could mean sprites
going on about the scores, whereas that shouldn't be possible.
Signed-off-by: Miquel Sabaté Solà <mssola@mssola.com>
Initialize enemies at a random Y coordinate2025-05-16T05:55:56ZMiquel Sabaté Solàmikisabate@gmail.com2025-05-15T20:06:00Zurn:sha1:638dfdca6e773d4b1ec573606cac90bdb1778667
The randomness comes from a pre-computed table of "random" numbers. This
is of course the most simple technique you can come across a code base
for the NES/Famicom, but for the purposes of this game is good enough
and (most importantly) fast.
Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
Don't touch zp_arg2 on background checks2025-05-14T17:38:30ZMiquel Sabaté Solàmikisabate@gmail.com2025-05-14T14:04:47Zurn:sha1:c9a37d15e270ef28b0048eba7cdab15b73b20331
This was a leftover from a previous implementation and is no longer
needed. Moreover, I have also added a comment clarifying that the 'y'
register is preserved.
Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
player: Implement background collision2025-04-01T19:21:27ZMiquel Sabaté Solàmikisabate@gmail.com2025-03-21T14:02:49Zurn:sha1:bcece25da4af0d4f47dc279dd5e1a67cb553186f
This adds a first implementation of collision checks between the player
and the background.
Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
Expanded ground collision to the other platforms2025-03-18T15:56:23ZMiquel Sabaté Solàmikisabate@gmail.com2025-03-18T15:56:23Zurn:sha1:d38a958f446aac1a6faa79277c140ab8a0ff03f4
This comes with a more general approach to handle background collision.
Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>