Bugs:Castlevania (NES)
This page details bugs of Castlevania (NES).
FDS Version
Staircase Glitch
There's a glitch present which can trigger an invisible staircase right before you meet Dracula. It appears that you are somehow able to "catch" the stairs a few pixels off on the screen below, which ultimately results in Simon walking up an invisible staircase into a screen of glitchy graphics. This bug was fixed for the cartridge-based versions. Later games, such as Super Castlevania IV and Akumajou Dracula X: Chi no Rondo, would pay tribute to this glitch with invisible or hidden stairs leading to secret rooms or bonuses.
Dracula Scoring
In the Disk System version, defeating Dracula's second form awards the player with 5 points instead of the intended 50,000 points due to a programming oversight. This was changed to the correct amount in the later cartridge versions.
Cartridge Versions
NMI Crash
Due to a simple oversight during the FDS to NES cartridge conversion, revision 0 of the game may crash in areas with lots of sprites, such as stage 15 (particularly the hallway below Death's chamber, and the battle with Death himself).
Normally when a non-maskable interrupt (NMI) is triggered at the end of a frame, ROM bank 0 is loaded at $8000-$BFFF, which contains some routines that are run during an NMI. However, if an NMI hits while the game is doing lots of sprite calculations, ROM bank 6 may be loaded instead; as a result, the game eventually jumps into the middle of the wrong routine and overwrites a large portion of RAM with garbage.
Revision 1 fixes this problem by swapping in bank 0 before attempting to jump to the offending routine.
The initial release of Castlevania Anniversary Collection mistakenly uses the Revision 0 ROM which has the aforementioned NMI glitch still intact.
Invisibility Potion Crash
Entering a door while under the effects of an invisibility potion can cause the game to crash in a similar manner to the "NMI crash" explained above. If the potion starts to wear off (RAM address $5B changes to $40) as Simon is passing through the door, the game attempts to jump to code in the switchable ROM area while the wrong bank is loaded, causing the CPU to hang on an invalid opcode. It's currently unclear why the crash only happens under these specific circumstances.
Interestingly, due to some code being moved around, the bug does not cause a crash in the Japanese cartridge release, though it will often spawn an invisible, glitchy solid object somewhere on the screen after the door transition.
Sound Fix
When Simon is falling into stage 10, the dropping sound starts a few frames before he appears on the screen. This was fixed in Revision 1 by moving the code that plays the sound ahead in the program.
No Music
If you let the first two demos play and then skip the third one and begin playing, there will be no music. The effect disappears if you die or reach the boss.
All Versions
Scroll Glitch
Caused by the way in which the game updates the level layout as you move. The game only checks if it should update the level layout every second frame, which means that if you only move on the frames in which the game doesn't check this the old layout data will be kept. While it's mostly used by the TAS due to the amount of precise inputs needed to move in this way, it can still be used sporadically in real time speedruns.
Unobtainable Money Bag
At the end of stage 9, right before the Mummy fight, pushing left against the block shown in the screenshot for several seconds will reveal a hidden money bag. Unfortunately, it is placed several blocks lower than it should be, and cannot be obtained normally (unless using the Scroll Glitch above).
How to Get
One possible solution is to use Scroll Glitch to keep a segment of "two platforms" layout near the position of money bag. But since a platform in boss room blocks the jumping route back directly, the player shall let a Medusa Head spawn and take damage to return above with the knockback (which cannot be done in easy mode).
Invisibility Potion Color Bug
At the end of the underground area of stage 10, touching the stairs while under the effects of an invisibility potion will cause Simon to retain his light blue outline in stage 11. The effect will last until Simon either dies or touches the orb at the end of the stage.
Screen Transition Bug
At the end of the underground area of stage 10, it's possible for Simon to get pushed upwards through the platform below the stairs by hitting a bat at the peak of his jump. When this happens, touching the stairs will cause the stage transition to fail (the stair-climbing animation expects a specific RAM variable to be set to #$00 to work properly; this variable is set to #$FF and not cleared at the end of Simon's hitstun animation). In the FDS and Japanese cartridge versions, this will freeze the game at a black screen; in the US cartridge versions, however, this will dump Simon in a glitched room with several sprites. Dying here will cause him to respawn in the correct area. Jumping or whipping before touching the stairs will allow the transition to proceed normally, as this resets the offending RAM variable that causes it to fail.
Broken Moai Head Animation
The spinning Moai Head bonus item found in the second loop of the game has a broken animation; the two halves of the sideways-facing sprite are squished together.
Second Loop Stage Counter
The stage counter does not reset when you begin the second loop. You start on Stage 19, but due to an oversight there is a small difference in the stage numbering. Stage 19 is the area outside of the castle and Stage 20 is the interior. In the first loop, both of these areas together were Stage 1. This results in Block 1 consisting of four stages instead of three in the second loop.
