Topic: Here's how to edit NES Castlevania's hidden items

[TheouAegis]

I'm sure some of you will be happy that I was working with the US release, which I'm sure is what 99% of modders are using.

Open the US ROM and jump to address $018048. It should be 0xB6DA1A00. This is the very first hidden item in the game. Each set of items is terminated by 0xFF, so you could potentially have 8 hidden items per stage. The status of a hidden item is bitmasked in RAM address $0144. The neighboring RAM address $0145 is used to keep track of how long Simon stays in place when necessary.

Here are the pointers for each stage (excluding Hard Mode numbering). This address map can be found at 0x01FC48 in the US ROM. Add #018010 to each pointer to find its corresponding address in the ROM. A lot of these just point to terminal #FF.

8038	Stage 00
804A	Stage 01
8041	Stage 02
804F	Stage 03
83FB	Stage 04
8400	Stage 05
8409	Stage 06
8556	Stage 07
8548	Stage 08
8551	Stage 09
87A0	Stage 10
87A0	Stage 11
87A0	Stage 12
89AF	Stage 13
89B4	Stage 14
89C0	Stage 15
8AE5	Stage 16
8AE1	Stage 17
8B39	Stage 18

Item definitions are in the following bitmasked format:
YYYYDMML XXXXXSSS VVVVHHHH IIIIIIII

Y = Y-coordinate
D = Difficulty
M = Mode
L = Level
X = X-coordinate
S = Screen (i.e., X div 256)
V = Vertical offset
H = Horizontal offset
I = Item number

Both X and Y are handled as-is (no arithmetic) and correspond to where Simon must posture. In other words, Y is always a multiple of 16 and X is a multiple of 8. Both V and H can be thought of in terms of 16*V or 16*H and refer to the position the item itself will spawn, relative to Simon.

There are 4 modes. Mode 0 requires Simon to stand still for 2 seconds. Mode 1 is just a quick duck at the spawn zone. Mode 2 requires Simon to stay in place while holding left or right for 2 seconds (this can be done while ducking, or by walking into a wall). Mode 3 just means Simon merely has to walk over the spawn area.

The Item numbers are as follows. Note that descriptions are based on Stage 04's sprites.

#00	Coins
#01	1UP
#02	Crown
#03	Chest
#04	Moai

I haven't found a way to get the shoes, coffee, kittens, or love letter. Then again, I didn't really take the time to test out all 256 possible item numbers.

[X]

shoes, coffee, kittens, or love letter

These I did not know about. The rest I apparently did as they were indicated on game maps.

[TheouAegis]

They were mentioned on The Cutting Room Floor. All of them are available in any screen that has the crown or moai sprites loaded. They were never used, and since I gave up trying to find them after 20 or so attempts, they probably wouldn't have any effect even if you could find the proper sprite definitions.

BTW I realized I left out the address for where the pointers are. I'll fix that tonight.