Sabreman fights with a bolt he throws, and it can harm only one kind of thing: what falls from the sky. Everything that lives in a room -- spiders, heads, spikes, the still hazards that line the paths -- is beyond it, to be walked round or jumped. This page is the bolt, the things from the sky, the score, and what makes a thing deadly. Knight Lore has none of it but the puff, its sparkle.

The bolt

FIRE runs in the player's turn. A fire key newly pressed (FIRE_HELD makes it one bolt a press) takes the first free of the two bolt records, copies the legs' record into it and makes it graphic 150, moving eight units a turn the way he faces (BOLT_STEPS, by GET_SPRITE_DIR), starting two steps -- 16 units -- ahead of him and 4 higher, with flags $14 and a half-height of 8. A start outside the room's walls (he is in a doorway, or facing a wall close up) is taken back. Then BOLT flies it: the fall and the cut (DEC_DZ_AND_UPDATE_UVZ) as for anything, but never below Z 132, so it flies level; its graphic cycles 151, 150, 149; it tests the two things from the sky (BOLT_HIT) and shoots one down if it touches it; and if its move was cut short in U or V by anything else it becomes a puff (START_PUFF), graphics 64 to 71 a turn each (PUFF, END_PUFF; the animations page plays it), and then nothing.

Facing	Way	Step in U	Step in V	Starts at U +	Starts at V +
0	-U	-8	0	-16	0
1	+U	8	0	16	0
2	+V	0	8	0	16
3	-V	0	-8	0	-16

Fired in room 30, which is empty, facing -U from the middle, in a simulator when this page was built:

Turn	Graphic		U	V	Z
0	149	the bolt	112	128	132
1	151	the bolt	104	128	132
2	150	the bolt	96	128	132
3	149	the bolt	88	128	132
4	151	the bolt	80	128	132
5	150	the bolt	72	128	132
6	64	the puff	70	128	132	stopped in U (+$0C bit 0)
7	65	the puff	70	128	132	stopped in U (+$0C bit 0)
8	66	the puff	70	128	132	stopped in U (+$0C bit 0)
9	67	the puff	70	128	132	stopped in U (+$0C bit 0)
10	68	the puff	70	128	132	stopped in U (+$0C bit 0)
11	69	the puff	70	128	132	stopped in U (+$0C bit 0)
12	70	the puff	70	128	132	stopped in U (+$0C bit 0)
13	71	the puff	70	128	132	stopped in U (+$0C bit 0)

What a bolt can hit

BOLT_HIT tests only records 4 and 5, the things from the sky, and skips graphics below 8 and the puff: each axis, the distance between them no more than their half-sizes added, plus 2. Nothing else is a target. Anything else in the way is only an obstacle to the collision code, which cuts the bolt's move short and so makes it a puff -- the heads, the spiders and the still hazards carry on as if nothing happened. In room 6, from a place out of their way, a bolt thrown at one of the two pacing heads:

Turn	The bolt	The head (graphic, U, V)
0		93, 136, 112
1	graphic 149 at U 154	93, 136, 114
2	graphic 64 at U 149, stopped	93, 136, 116
3	graphic 65 at U 149, stopped	93, 136, 118
4	graphic 66 at U 149, stopped	93, 136, 120
5	graphic 67 at U 149, stopped	93, 136, 122
6	graphic 68 at U 149, stopped	93, 136, 124
7	graphic 69 at U 149, stopped	93, 136, 126
8	graphic 70 at U 149, stopped	93, 136, 128
9	graphic 71 at U 149, stopped	93, 136, 130

The bolts' test has one more use: the well counts the turns a bolt touches it (BOLT_TOUCHING, and see the quest).

What	Against	What happens	Where
A bolt	a thing from the sky	shot down: points, and it becomes a puff; the bolt vanishes	SHOOT_DOWN
A bolt	the well	a turn of contact counted; 32 in one visit give the bucket	WELL
A bolt	anything else, or a wall	its move is cut short, and it becomes a puff	BOLT
Anything deadly (+$0D bit 7)	what it moves into	killed (+$0D bit 6)	ADJ_DU_FOR_OBJ_INTERSECT
Anything deadly (+$0D bit 5)	what moves into it	killed	ADJ_DU_FOR_OBJ_INTERSECT
A thing from the sky that homes	the player	nothing: it is not deadly	HOMER

Things from the sky

Every turn SKY_DROP counts DROP_TIMER down (it is reset at each room's start and after each drop, by RESET_DROP_TIMER -- 80 turns, or 8 once the first quest item is done: see the quest page). When it has run out, there is a chance of one in four each turn, two bits of the random number, of a drop: a free one of the two records at FLYERS gets a copy of FLYER_TEMPLATE -- Z 216, half-sizes 8, 8 and 8, flags $10 -- a U and a V of 104 plus a random number masked with $2F (104 to 119 or 136 to 151: never on the room's middle lines), and one of the eight graphics at DROP_GRAPHICS picked by three more bits of the random number. If it would overlap anything it is taken back. Nothing falls at all in a room with the well, a quest item or a piece of the pentagram (BAN_DROPS; 7 rooms as the game starts, and room 82 once the pentagram is showing).

Slot	Graphic	Sprite	Update routine	Deadly	Points, by frame
0	164		HOMER	no	512, 516
1	160		HOMER	no	502, 506
2	48		HOMER	no	140, 144
3	80		SKY_ROAMER	yes	241, 245
4	168		SKY_WALKER	yes	522, 526
5	160		HOMER	no	502, 506
6	48		HOMER	no	140, 144
7	80		SKY_ROAMER	yes	241, 245

HOMER, the homer, flies at him: a speed in each of U, V and Z kept in sixteenths, each pulled 3 a turn towards his legs' U and V and his body's Z, up to 56 or down to -72, and a step each turn of the speed plus 8 over 16 -- at most 4 units either way; bumping into anything in U or V turns that speed round, so it bounces. It is never deadly: no update routine of a homer sets a kill bit, and its record starts with a clear +$0D. ROAMER (graphics 80 and 81, at SKY_ROAMER) and SKY_WALKER (168 to 171) are the ones that kill: they fall, then run straight at 4 a turn, turning at a bump, deadly both ways.

That chance is less of one than it looks. OBJECT_DONE stirs the random number once per object, with R and the turn counter, and with interrupts off nothing else touches R: a turn in which nothing changes runs exactly the instructions the turn before did. In room 30, empty, with the timer run out and the player standing still, the random number was read at the test for 150 turns: it moved by an even amount every turn, so its lowest bit never changed; it was odd, the test wants both low bits clear, and nothing fell. That was in the simulator; the same should hold on a Spectrum, whose R counts instructions the same way, but that is inferred. Anything that changes the turn's path -- turning, walking, firing -- stirs it again.

In room 30 again, with the drop timer run out by writing it, the player turning a quarter every six turns and, once something had fallen, firing between turns: a homer, graphic 165, fell 85 turns in, from Z 215 at (108, 145). It homed on him and hung round him for 39 turns without harming him, until a bolt hit it, at graphic 167, for 516 points:

Turns after the drop	Graphic	U	V	Z	Speeds U, V, Z	Score
0	165	108	145	215	3, -3, -3	0
6	167	112	141	205	21, -21, -21	0
12	165	123	131	189	39, -39, -39	0
18	167	138	118	166	33, -27, -57	0
24	165	148	111	136	15, -9, -69	0
30	167	151	110	128	-3, 9, -51	0
36	165	147	117	128	-21, 27, -33	0
38	167	145	121	128	-27, 33, -27	0
39	65	145	121	128	-27, 33, -27	516

The score

SHOOT_DOWN makes the points out of the graphic number of what was hit, bits into BCD digits: the hundreds from bits 5 to 7, the tens from bits 2 to 4, the units from bits 6, 7 and 0. No digit can pass 7, so the result is always good BCD without a check. ADD_SCORE adds them and SHOW_SCORE copies the score straight to the screen. Things animate by changing their graphic, so the points depend on the frame the bolt catches. Run on its own for every graphic a thing from the sky can have:

What	Graphics	Points
homers	48-51, 160-167	48: 140, 49: 144, 50: 140, 51: 144, 160: 502, 161: 506, 162: 502, 163: 506, 164: 512, 165: 516, 166: 512, 167: 516
the creature that roams	80-81	80: 241, 81: 245
the walker	168-171	168: 522, 169: 526, 170: 522, 171: 526

What makes a thing deadly

Two bits of +$0D: bit 7, kills what it moves into, and bit 5, kills what touches it. MAKE_DEADLY sets both, and the collision code (ADJ_DU_FOR_OBJ_INTERSECT and the other two axes) passes the kill -- bit 6 -- to whichever party the other's bits say. These are all the routines that call it, found by searching the code for the call, with the graphics the update table gives them and the rooms that place those:

Routine	Graphics	Where
STILL_DEADLY	23, 30, 74-75	73 rooms, from 0, 1, 2, 4, 5, 7, 12, 13, 15, 16, 18, 20 ...
DEADLY_AND_DRAW	none (unreached)
SPIKES	28	rooms 8, 14, 19, 41, 76, 103, 111
DEADLY_BOBBER	86	rooms 11, 27, 42, 55, 62, 88, 107, 108
DEADLY_PACER_U	92	rooms 29, 34, 47, 83, 99, 120, 130
DEADLY_PACER_V	93	rooms 6, 29, 49, 129, 147
SPIDER	89	16 rooms, from 3, 9, 13, 14, 15, 24, 26, 53, 69, 98, 106, 109 ...
ROAMER	16-17, 80-81	rooms 20, 52, 76, 96, 106, 117, 125, 131; and from the sky
SKY_WALKER	168-171	no room; and from the sky

A killed player's legs become the puff and his body with them; when the puff is over, both records are empty and the main loop starts a life (see rooms and doorways for where).

Confirmed and inferred

• Run in the simulator when this page was built: the bolt's flight and puff, the bolt against the head, the drop, the homer's flight and its harmlessness over those turns, the shot and its points, and the score for every graphic.
• Staged: the player's facing and place, written into his record; the drop timer, written to 1. Everything after is the game's.
• Read from the code: the one-in-four chance, the random place and graphic, the bans; the homer's speeds; that the roamer and the walker kill.