A Documenting of mine Enhanced Enchantment CHIP-8 Game
This is my first game for the Octo Jam 7 event. I've improved mine Enchantment game from 2020-06-30
nicely, with great line variety. Follows is a view of the complete game, when loaded into mine MMC:
200-201 0512-0513 ▀▄▀ ▄ ▀▀ A348 41800 I ← from
202-203 0514-0515 ▀██▀▀█▀█ FF65 65381 Load V0→VF; I ← I + 16
204-205 0516-0517 ▀ █ ▄▄▀ A22C 41516 I ← ball
206-207 0518-0519 ▀█▄█ ▀▀▄ D671 54897 Draw 08×01 at V6,V7; VF ← XOR
208-209 0520-0521 ▀▀ ▄██▄ CC1E 52254 VC ← ??? AND 030
20A-20B 0522-0523 ▀▀ ▄██▄▀ CD1E 52510 VD ← ??? AND 030
20C-20D 0524-0525 ▀▀▀█ ▄ █ F115 61717 movement delay ← V1
20E-20F 0526-0527 ▀▀ ████ 6F0F 28431 VF ← 015
210-211 0528-0529 █▀█ ▀▀▀█ EFA1 61345 Skip next if VF <> key
212-213 0530-0531 ▀▀▀▀█▀█▀ FF0A 65290 VF ← key
214-215 0532-0533 ▀█▄█ ▀▀▄ D671 54897 Draw 08×01 at V6,V7; VF ← XOR
216-217 0534-0535 █▀█ ▄ E0A1 57505 Skip next if V0 <> key
218-219 0536-0537 ▀▀▀ ▀▀▄ 7601 30209 V6 ← V6 + 001
21A-21B 0538-0539 █▀█ █ E1A1 57761 Skip next if V1 <> key
21C-21D 0540-0541 ▄███▄██▄ 76FF 30463 V6 ← V6 + 255
21E-21F 0542-0543 █▀█ ▀▄ E2A1 58017 Skip next if V2 <> key
220-221 0544-0545 ▀▀▀ ▀▀█ 7701 30465 V7 ← V7 + 001
222-223 0546-0547 █▀█ ▀█ E3A1 58273 Skip next if V3 <> key
224-225 0548-0549 ▄███▄███ 77FF 30719 V7 ← V7 + 255
226-227 0550-0551 ▀▄ ▀█ 8642 34370 V6 ← V6 AND V4
228-229 0552-0553 ▀▄ ▄ ▀█▀ 8752 34642 V7 ← V7 AND V5
22A-22B 0554-0555 ▀█▄█ ▀▀▄ D671 54897 Draw 08×01 at V6,V7; VF ← XOR
22C-22D 0556-0557 █▄ 80C0 32960+ ball V0 ← VC
22E-22F 0558-0559 ▀▀ ▀ 6200 25088 V2 ← 000
230-231 0560-0561 █ ▀▀ 8380 33664 V3 ← V8
232-233 0562-0563 █ ▄ ▀ 8490 33936 V4 ← V9
234-235 0564-0565 ▀ ▀▀▀▀ 4F00 20224 Skip next if VF <> 000
236-237 0566-0567 ▀▄▀▀ ▄█ B246 45638 Jump to V0 + table
238-239 0568-0569 ▄▄▄ 00E0 00224 Clear the screen
23A-23B 0570-0571 ▀ ▀ 1200 04608 Jump to 0512
23C-23D 0572-0573 █▄ ▄ 80D0 32976 second V0 ← VD
23E-23F 0574-0575 ▀▀ ▀▄ 6201 25089 V2 ← 001
240-241 0576-0577 █ ▄ ▀▀ 83A0 33696 V3 ← VA
242-243 0578-0579 █ ▄▄ ▀ 84B0 33968 V4 ← VB
244-245 0580-0581 ▀▄▀▀ ▄█ B246 45638 Jump to V0 + table
246-247 0582-0583 ▄▄▀▄ █ 126A 04714 table Jump to up left
248-249 0584-0585 ▄▄█ ▀ 1270 04720 Jump to up right
24A-24B 0586-0587 ▄▄█ ▄█ 1276 04726 Jump to down left
24C-24D 0588-0589 ▄▄█▄▄▀ 127C 04732 Jump to down right
24E-24F 0590-0591 ▄ ▀ █ 1282 04738 Jump to left up
250-251 0592-0593 ▄ ▀▄ ▀ 1288 04744 Jump to left down
252-253 0594-0595 ▄ ▀▄▄█ 128E 04750 Jump to right up
254-255 0596-0597 ▄ █ ▄▀ 1294 04756 Jump to right down
256-257 0598-0599 ▄ █▄ █ 129A 04762 Jump to two up left
258-259 0600-0601 ▄ ▄▀ █ 12A2 04770 Jump to two up right
25A-25B 0602-0603 ▄ ▄▀▄ █ 12AA 04778 Jump to two down left
25C-25D 0604-0605 ▄ ▄█ █ 12B2 04786 Jump to two down right
25E-25F 0606-0607 ▄ ▄█▄ █ 12BA 04794 Jump to two left up
260-261 0608-0609 ▄▄ ▀ █ 12C2 04802 Jump to two right down
262-263 0610-0611 ▄▄ ▀▄ █ 12CA 04810 Jump to left targeting
264-265 0612-0613 ▄▄ ▀▄▄▀ 12CC 04812 Jump to right targeting
266-267 0614-0615 ▄▄ █▄▄█ 12DE 04830 Jump to up
268-269 0616-0617 ▄▄▄▀ ▀ 12E0 04832 Jump to down
26A-26B 0618-0619 ▄███▄▄██ 73FF 29695 up left V3 ← V3 + 255
26C-26D 0620-0621 ▀▀▀ ▀ ▄ 7401 29697 V4 ← V4 + 001
26E-26F 0622-0623 ▄▄▄▀ █ 12E2 04834 Jump to integrate
270-271 0624-0625 ▀▀▀ ▀█ 7301 29441 up right V3 ← V3 + 001
272-273 0626-0627 ▀▀▀ ▀ ▄ 7401 29697 V4 ← V4 + 001
274-275 0628-0629 ▄▄▄▀ █ 12E2 04834 Jump to integrate
276-277 0630-0631 ▄███▄▄██ 73FF 29695 down left V3 ← V3 + 255
278-279 0632-0633 ▄███▄█▄▄ 74FF 29951 V4 ← V4 + 255
27A-27B 0634-0635 ▄▄▄▀ █ 12E2 04834 Jump to integrate
27C-27D 0636-0637 ▀▀▀ ▀█ 7301 29441 down right V3 ← V3 + 001
27E-27F 0638-0639 ▄███▄█▄▄ 74FF 29951 V4 ← V4 + 255
280-281 0640-0641 ▄▄▄▀ █ 12E2 04834 Jump to integrate
282-283 0642-0643 ▀▀▀ ▀█ 7301 29441 left up V3 ← V3 + 001
284-285 0644-0645 ▄███▄█▄▄ 74FF 29951 V4 ← V4 + 255
286-287 0646-0647 ▄▄▄▀ █ 12E2 04834 Jump to integrate
288-289 0648-0649 ▀▀▀ ▀█ 7301 29441 left down V3 ← V3 + 001
28A-28B 0650-0651 ▀▀▀ ▀ ▄ 7401 29697 V4 ← V4 + 001
28C-28D 0652-0653 ▄▄▄▀ █ 12E2 04834 Jump to integrate
28E-28F 0654-0655 ▄███▄▄██ 73FF 29695 right up V3 ← V3 + 255
290-291 0656-0657 ▄███▄█▄▄ 74FF 29951 V4 ← V4 + 255
292-293 0658-0659 ▄▄▄▀ █ 12E2 04834 Jump to integrate
294-295 0660-0661 ▄███▄▄██ 73FF 29695 right down V3 ← V3 + 255
296-297 0662-0663 ▀▀▀ ▀ ▄ 7401 29697 V4 ← V4 + 001
298-299 0664-0665 ▄▄▄▀ █ 12E2 04834 Jump to integrate
29A-29B 0666-0667 ▄███▄▄█▀ 73FE 29694 two up left V3 ← V3 + 254
29C-29D 0668-0669 ▀▀▀ ▀ ▄ 7401 29697 V4 ← V4 + 001
29E-29F 0670-0671 ▀ █ ▄▄▀▄ A22D 41517 I ← two balls
2A0-2A1 0672-0673 ▄▄▄▀ █ 12E2 04834 Jump to integrate
2A2-2A3 0674-0675 ▀▀▀ █▀ 7302 29442 two up right V3 ← V3 + 002
2A4-2A5 0676-0677 ▀▀▀ ▀ ▄ 7401 29697 V4 ← V4 + 001
2A6-2A7 0678-0679 ▀ █ ▄▄▀▄ A22D 41517 I ← two balls
2A8-2A9 0680-0681 ▄▄▄▀ █ 12E2 04834 Jump to integrate
2AA-2AB 0682-0683 ▄███▄▄█▀ 73FE 29694 two down left V3 ← V3 + 254
2AC-2AD 0684-0685 ▄███▄█▄▄ 74FF 29951 V4 ← V4 + 255
2AE-2AF 0686-0687 ▀ █ ▄▄▀▄ A22D 41517 I ← two balls
2B0-2B1 0688-0689 ▄▄▄▀ █ 12E2 04834 Jump to integrate
2B2-2B3 0690-0691 ▀▀▀ █▀ 7302 29442 two down right V3 ← V3 + 002
2B4-2B5 0692-0693 ▄███▄█▄▄ 74FF 29951 V4 ← V4 + 255
2B6-2B7 0694-0695 ▀ █ ▄▄▀▄ A22D 41517 I ← two balls
2B8-2B9 0696-0697 ▄▄▄▀ █ 12E2 04834 Jump to integrate
2BA-2BB 0698-0699 ▀▀▀ █▀ 7302 29442 two left up V3 ← V3 + 002
2BC-2BD 0700-0701 ▀▀▀ ▀ ▄ 7401 29697 V4 ← V4 + 001
2BE-2BF 0702-0703 ▀ █ ▄▄▀▄ A22D 41517 I ← two balls
2C0-2C1 0704-0705 ▄▄▄▀ █ 12E2 04834 Jump to integrate
2C2-2C3 0706-0707 ▄███▄▄█▀ 73FE 29694 two right down V3 ← V3 + 254
2C4-2C5 0708-0709 ▄███▄█▄▄ 74FF 29951 V4 ← V4 + 255
2C6-2C7 0710-0711 ▀ █ ▄▄▀▄ A22D 41517 I ← two balls
2C8-2C9 0712-0713 ▄▄▄▀ █ 12E2 04834 Jump to integrate
2CA-2CB 0714-0715 ▄███▄▄█▀ 73FE 29694 left targeting V3 ← V3 + 254
2CC-2CD 0716-0717 ▀▀▀ ▀█ 7301 29441 right targeting V3 ← V3 + 001
2CE-2CF 0718-0719 █▄▀ ▀▀ 5360 21344 Skip next if V3 = V6
2D0-2D1 0720-0721 ▄▄▄▀ █ 12E2 04834 Jump to integrate
2D2-2D3 0722-0723 ▀▄ ▀ 8140 33088 V1 ← V4
2D4-2D5 0724-0725 ▀▄▄▄ ▄ █ 8175 33141 V1 ← V1 − V7; VF ← borrow
2D6-2D7 0726-0727 ▀█ 6020 24608 V0 ← 032
2D8-2D9 0728-0729 ▀ ▀▀▀▀ 4F00 20224 Skip next if VF <> 000
2DA-2DB 0730-0731 ▀█ ▄ 6022 24610 V0 ← 034
2DC-2DD 0732-0733 ▄▄▄▀ █ 12E2 04834 Jump to integrate
2DE-2DF 0734-0735 ▄███▄█▄ 74FE 29950 up V4 ← V4 + 254
2E0-2E1 0736-0737 ▀▀▀ ▀ ▄ 7401 29697 down V4 ← V4 + 001
2E2-2E3 0738-0739 ▀▀▀▀ ▄▄█ F107 61703 integrate V1 ← delay
2E4-2E5 0740-0741 ▀▀ ▀ 3100 12544 Skip next if V1 = 000
2E6-2E7 0742-0743 ▄▄▄▀ █ 12E2 04834 Jump to integrate
2E8-2E9 0744-0745 ▄█▄▄▄▄█▀ 43FE 17406 Skip next if V3 <> 254
2EA-2EB 0746-0747 ▄█ ▄█▀ 1336 04918 Jump to new line
2EC-2ED 0748-0749 ▄█▄▄▄█▄ 44FE 17662 Skip next if V4 <> 254
2EE-2EF 0750-0751 ▄█ ▄█▀ 1336 04918 Jump to new line
2F0-2F1 0752-0753 ▄█▄▄▄▄██ 43FF 17407 Skip next if V3 <> 255
2F2-2F3 0754-0755 ▄█ ▄█▀ 1336 04918 Jump to new line
2F4-2F5 0756-0757 ▄█▄▄▄█▄▄ 44FF 17663 Skip next if V4 <> 255
2F6-2F7 0758-0759 ▄█ ▄█▀ 1336 04918 Jump to new line
2F8-2F9 0760-0761 █ ▀█ 4341 17217 Skip next if V3 <> 065
2FA-2FB 0762-0763 ▄█ ▄█▀ 1336 04918 Jump to new line
2FC-2FD 0764-0765 ▀▄ ▀ ▄ 4421 17441 Skip next if V4 <> 033
2FE-2FF 0766-0767 ▄█ ▄█▀ 1336 04918 Jump to new line
300-301 0768-0769 █ ▀▀ 4340 17216 Skip next if V3 <> 064
302-303 0770-0771 ▄█ ▄█▀ 1336 04918 Jump to new line
304-305 0772-0773 ▀▄ ▀ 4420 17440 Skip next if V4 <> 032
306-307 0774-0775 ▄█ ▄█▀ 1336 04918 Jump to new line
308-309 0776-0777 ▀█ ▀ ▀█ D341 54081 Draw 08×01 at V3,V4; VF ← XOR
30A-30B 0778-0779 ▀ ▀▀ 4300 17152 Skip next if V3 <> 000
30C-30D 0780-0781 ▄█ ▄█▀ 1336 04918 Jump to new line
30E-30F 0782-0783 ▀▄▄▄▄██ 433F 17215 Skip next if V3 <> 063
310-311 0784-0785 ▄█ ▄█▀ 1336 04918 Jump to new line
312-313 0786-0787 ▀ ▀ 4400 17408 Skip next if V4 <> 000
314-315 0788-0789 ▄█ ▄█▀ 1336 04918 Jump to new line
316-317 0790-0791 ▀ ▄▄█▄▄ 441F 17439 Skip next if V4 <> 031
318-319 0792-0793 ▄█ ▄█▀ 1336 04918 Jump to new line
31A-31B 0794-0795 ▀ █ ▄▄▀ A22C 41516 dispatch I ← ball
31C-31D 0796-0797 ▀▀ ▀ 3200 12800 Skip next if V2 = 000
31E-31F 0798-0799 ▄▀▄ ▀▀ 1328 04904 Jump to next
320-321 0800-0801 ▀ ▀▀ 8C00 35840 VC ← V0
322-323 0802-0803 ▀ ▄▄▀ 8830 34864 V8 ← V3
324-325 0804-0805 ▀▄ ▀ ▀ 8940 35136 V9 ← V4
326-327 0806-0807 ▄█▄▄▀ 123C 04668 Jump to second
328-329 0808-0809 ▀ ▀▀ ▀ 8D00 36096 next VD ← V0
32A-32B 0810-0811 ▀ ▄▄▀ ▀ 8A30 35376 VA ← V3
32C-32D 0812-0813 ▀▄ ▀ ▀▀ 8B40 35648 VB ← V4
32E-32F 0814-0815 ▀▄▀ ▄ ▀▀ A348 41800 I ← from
330-331 0816-0817 ▀██▀ █ ▄ F465 62565 Load V0→V4; I ← I + 05
332-333 0818-0819 ▀ █ ▄▄▀ A22C 41516 I ← ball
334-335 0820-0821 ▀▄▄▀ 120C 04620 Jump to movement
336-337 0822-0823 ▀▀ ▄▄▄▄ C01E 49182 new line V0 ← ??? AND 030
338-339 0824-0825 ▀▀ █ C101 49409 V1 ← ??? AND 001
33A-33B 0826-0827 ▀▀▄▄▄▄██ C33F 49983 V3 ← ??? AND 063
33C-33D 0828-0829 ▀▀ ▄▄█▄▄ C41F 50207 V4 ← ??? AND 031
33E-33F 0830-0831 ▀▀ ▀ 3100 12544 Skip next if V1 = 000
340-341 0832-0833 ▀▀ ▀▀ 6300 25344 V3 ← 000
342-343 0834-0835 ▀ ▀ 4100 16640 Skip next if V1 <> 000
344-345 0836-0837 ▀▀ ▀ 6400 25600 V4 ← 000
346-347 0838-0839 █▄ █▀ 131A 04890 Jump to dispatch
348 0840 ██ 06 006 from
349 0841 █ 04 004
34A 0842 █ 02 002
34B 0843 █ 08 008
34C 0844 ██████ 3F 063
34D 0845 █████ 1F 031
34E 0846 █████ 1F 031
34F 0847 ████ 0F 015
The register usage is as follows:
V0 Right movement button and holding the identifier code.
V1 Left movement button, delay, and miscellaneous storage.
V2 Down movement button and first or second line boolean.
V3 Up movement button.
V4 Horizontal mask.
V5 Vertical mask.
V6 Horizontal coordinate of player.
V7 Vertical coordinate of player.
V8 Horizontal coordinate of first line.
V9 Vertical coordinate of first line.
VA Horizontal coordinate of second line.
VB Vertical coordinate of second line.
VC Identifier code of first line.
VD Identifier code of second line.
VE Unused.
VF Collision detection and holding a key code.
The registers were chosen for the following reasons:
V0 Ease of access.
V1 Ease of access.
V2 Ease of access.
V3 Ease of access.
V4 Ease of access.
V5 It follows V4.
V6 It's even.
V7 It follows V6.
V8 It follows the V6 and V7 pattern.
V9 It follows the V6 and V7 pattern.
VA It follows the V6 and V7 pattern.
VB It follows the V6 and V7 pattern.
VC It's even.
VD It follows VC.
VE Unused.
VF Unimportance and necessity.
The game begins by initializing the registers and setting I to its primary value. The player sprite
is drawn and both line identifier registers are initialized to random values. Note that this chosen
mask results in sixteen distinct values which will always be even, perfectly suitable for the table:
200-201 0512-0513 ▀▄▀ ▄ ▀▀ A348 41800 I ← from
202-203 0514-0515 ▀██▀▀█▀█ FF65 65381 Load V0→VF; I ← I + 16
204-205 0516-0517 ▀ █ ▄▄▀ A22C 41516 I ← ball
206-207 0518-0519 ▀█▄█ ▀▀▄ D671 54897 Draw 08×01 at V6,V7; VF ← XOR
208-209 0520-0521 ▀▀ ▄██▄ CC1E 52254 VC ← ??? AND 030
20A-20B 0522-0523 ▀▀ ▄██▄▀ CD1E 52510 VD ← ??? AND 030
The delay is set and then the player movement is calculated; the fifteenth key works as a pause key,
with movement in the cardinal directions being the only other options. The new position is ANDed to
maintain bounds. This code results in the player sprite flickering, but such is desirable for this:
20C-20D 0524-0525 ▀▀▀█ ▄ █ F115 61717 movement delay ← V1
20E-20F 0526-0527 ▀▀ ████ 6F0F 28431 VF ← 015
210-211 0528-0529 █▀█ ▀▀▀█ EFA1 61345 Skip next if VF <> key
212-213 0530-0531 ▀▀▀▀█▀█▀ FF0A 65290 VF ← key
214-215 0532-0533 ▀█▄█ ▀▀▄ D671 54897 Draw 08×01 at V6,V7; VF ← XOR
216-217 0534-0535 █▀█ ▄ E0A1 57505 Skip next if V0 <> key
218-219 0536-0537 ▀▀▀ ▀▀▄ 7601 30209 V6 ← V6 + 001
21A-21B 0538-0539 █▀█ █ E1A1 57761 Skip next if V1 <> key
21C-21D 0540-0541 ▄███▄██▄ 76FF 30463 V6 ← V6 + 255
21E-21F 0542-0543 █▀█ ▀▄ E2A1 58017 Skip next if V2 <> key
220-221 0544-0545 ▀▀▀ ▀▀█ 7701 30465 V7 ← V7 + 001
222-223 0546-0547 █▀█ ▀█ E3A1 58273 Skip next if V3 <> key
224-225 0548-0549 ▄███▄███ 77FF 30719 V7 ← V7 + 255
226-227 0550-0551 ▀▄ ▀█ 8642 34370 V6 ← V6 AND V4
228-229 0552-0553 ▀▄ ▄ ▀█▀ 8752 34642 V7 ← V7 AND V5
22A-22B 0554-0555 ▀█▄█ ▀▀▄ D671 54897 Draw 08×01 at V6,V7; VF ← XOR
Conveniently, the 80C0 instruction functions as the ball and two balls sprites. The first line gets
its parameters copied and the game enters the jump table by the line identifier, unless the previous
player draw resulted in a collision, in which case the screen is cleared and the game is then reset:
22C-22D 0556-0557 █▄ 80C0 32960+ ball V0 ← VC
22E-22F 0558-0559 ▀▀ ▀ 6200 25088 V2 ← 000
230-231 0560-0561 █ ▀▀ 8380 33664 V3 ← V8
232-233 0562-0563 █ ▄ ▀ 8490 33936 V4 ← V9
234-235 0564-0565 ▀ ▀▀▀▀ 4F00 20224 Skip next if VF <> 000
236-237 0566-0567 ▀▄▀▀ ▄█ B246 45638 Jump to V0 + table
238-239 0568-0569 ▄▄▄ 00E0 00224 Clear the screen
23A-23B 0570-0571 ▀ ▀ 1200 04608 Jump to 0512
This fragment merely does the same for the second line:
23C-23D 0572-0573 █▄ ▄ 80D0 32976 second V0 ← VD
23E-23F 0574-0575 ▀▀ ▀▄ 6201 25089 V2 ← 001
240-241 0576-0577 █ ▄ ▀▀ 83A0 33696 V3 ← VA
242-243 0578-0579 █ ▄▄ ▀ 84B0 33968 V4 ← VB
244-245 0580-0581 ▀▄▀▀ ▄█ B246 45638 Jump to V0 + table
This is the jump table; notice neither up or down won't be selected by the mask, being out of range:
246-247 0582-0583 ▄▄▀▄ █ 126A 04714 table Jump to up left
248-249 0584-0585 ▄▄█ ▀ 1270 04720 Jump to up right
24A-24B 0586-0587 ▄▄█ ▄█ 1276 04726 Jump to down left
24C-24D 0588-0589 ▄▄█▄▄▀ 127C 04732 Jump to down right
24E-24F 0590-0591 ▄ ▀ █ 1282 04738 Jump to left up
250-251 0592-0593 ▄ ▀▄ ▀ 1288 04744 Jump to left down
252-253 0594-0595 ▄ ▀▄▄█ 128E 04750 Jump to right up
254-255 0596-0597 ▄ █ ▄▀ 1294 04756 Jump to right down
256-257 0598-0599 ▄ █▄ █ 129A 04762 Jump to two up left
258-259 0600-0601 ▄ ▄▀ █ 12A2 04770 Jump to two up right
25A-25B 0602-0603 ▄ ▄▀▄ █ 12AA 04778 Jump to two down left
25C-25D 0604-0605 ▄ ▄█ █ 12B2 04786 Jump to two down right
25E-25F 0606-0607 ▄ ▄█▄ █ 12BA 04794 Jump to two left up
260-261 0608-0609 ▄▄ ▀ █ 12C2 04802 Jump to two right down
262-263 0610-0611 ▄▄ ▀▄ █ 12CA 04810 Jump to left targeting
264-265 0612-0613 ▄▄ ▀▄▄▀ 12CC 04812 Jump to right targeting
266-267 0614-0615 ▄▄ █▄▄█ 12DE 04830 Jump to up
268-269 0616-0617 ▄▄▄▀ ▀ 12E0 04832 Jump to down
These line routines implement those which move one-by-one, beginning from the top or bottom:
26A-26B 0618-0619 ▄███▄▄██ 73FF 29695 up left V3 ← V3 + 255
26C-26D 0620-0621 ▀▀▀ ▀ ▄ 7401 29697 V4 ← V4 + 001
26E-26F 0622-0623 ▄▄▄▀ █ 12E2 04834 Jump to integrate
270-271 0624-0625 ▀▀▀ ▀█ 7301 29441 up right V3 ← V3 + 001
272-273 0626-0627 ▀▀▀ ▀ ▄ 7401 29697 V4 ← V4 + 001
274-275 0628-0629 ▄▄▄▀ █ 12E2 04834 Jump to integrate
276-277 0630-0631 ▄███▄▄██ 73FF 29695 down left V3 ← V3 + 255
278-279 0632-0633 ▄███▄█▄▄ 74FF 29951 V4 ← V4 + 255
27A-27B 0634-0635 ▄▄▄▀ █ 12E2 04834 Jump to integrate
27C-27D 0636-0637 ▀▀▀ ▀█ 7301 29441 down right V3 ← V3 + 001
27E-27F 0638-0639 ▄███▄█▄▄ 74FF 29951 V4 ← V4 + 255
280-281 0640-0641 ▄▄▄▀ █ 12E2 04834 Jump to integrate
These implement those beginning from the left or right:
282-283 0642-0643 ▀▀▀ ▀█ 7301 29441 left up V3 ← V3 + 001
284-285 0644-0645 ▄███▄█▄▄ 74FF 29951 V4 ← V4 + 255
286-287 0646-0647 ▄▄▄▀ █ 12E2 04834 Jump to integrate
288-289 0648-0649 ▀▀▀ ▀█ 7301 29441 left down V3 ← V3 + 001
28A-28B 0650-0651 ▀▀▀ ▀ ▄ 7401 29697 V4 ← V4 + 001
28C-28D 0652-0653 ▄▄▄▀ █ 12E2 04834 Jump to integrate
28E-28F 0654-0655 ▄███▄▄██ 73FF 29695 right up V3 ← V3 + 255
290-291 0656-0657 ▄███▄█▄▄ 74FF 29951 V4 ← V4 + 255
292-293 0658-0659 ▄▄▄▀ █ 12E2 04834 Jump to integrate
294-295 0660-0661 ▄███▄▄██ 73FF 29695 right down V3 ← V3 + 255
296-297 0662-0663 ▀▀▀ ▀ ▄ 7401 29697 V4 ← V4 + 001
298-299 0664-0665 ▄▄▄▀ █ 12E2 04834 Jump to integrate
These are kin to the first four, but move left or right two-at-a-time, changing the sprite for this:
29A-29B 0666-0667 ▄███▄▄█▀ 73FE 29694 two up left V3 ← V3 + 254
29C-29D 0668-0669 ▀▀▀ ▀ ▄ 7401 29697 V4 ← V4 + 001
29E-29F 0670-0671 ▀ █ ▄▄▀▄ A22D 41517 I ← two balls
2A0-2A1 0672-0673 ▄▄▄▀ █ 12E2 04834 Jump to integrate
2A2-2A3 0674-0675 ▀▀▀ █▀ 7302 29442 two up right V3 ← V3 + 002
2A4-2A5 0676-0677 ▀▀▀ ▀ ▄ 7401 29697 V4 ← V4 + 001
2A6-2A7 0678-0679 ▀ █ ▄▄▀▄ A22D 41517 I ← two balls
2A8-2A9 0680-0681 ▄▄▄▀ █ 12E2 04834 Jump to integrate
2AA-2AB 0682-0683 ▄███▄▄█▀ 73FE 29694 two down left V3 ← V3 + 254
2AC-2AD 0684-0685 ▄███▄█▄▄ 74FF 29951 V4 ← V4 + 255
2AE-2AF 0686-0687 ▀ █ ▄▄▀▄ A22D 41517 I ← two balls
2B0-2B1 0688-0689 ▄▄▄▀ █ 12E2 04834 Jump to integrate
2B2-2B3 0690-0691 ▀▀▀ █▀ 7302 29442 two down right V3 ← V3 + 002
2B4-2B5 0692-0693 ▄███▄█▄▄ 74FF 29951 V4 ← V4 + 255
2B6-2B7 0694-0695 ▀ █ ▄▄▀▄ A22D 41517 I ← two balls
2B8-2B9 0696-0697 ▄▄▄▀ █ 12E2 04834 Jump to integrate
To fit the targeting lines, the two-at-a-time left or right routines are uneven:
2BA-2BB 0698-0699 ▀▀▀ █▀ 7302 29442 two left up V3 ← V3 + 002
2BC-2BD 0700-0701 ▀▀▀ ▀ ▄ 7401 29697 V4 ← V4 + 001
2BE-2BF 0702-0703 ▀ █ ▄▄▀▄ A22D 41517 I ← two balls
2C0-2C1 0704-0705 ▄▄▄▀ █ 12E2 04834 Jump to integrate
2C2-2C3 0706-0707 ▄███▄▄█▀ 73FE 29694 two right down V3 ← V3 + 254
2C4-2C5 0708-0709 ▄███▄█▄▄ 74FF 29951 V4 ← V4 + 255
2C6-2C7 0710-0711 ▀ █ ▄▄▀▄ A22D 41517 I ← two balls
2C8-2C9 0712-0713 ▄▄▄▀ █ 12E2 04834 Jump to integrate
The targeting lines progress from the left or right until they align with the player, which then has
them switch their codes to up or down, based on the relative position of the player; originally, I'd
duplicated these routines, then combined them with a 5CC0, and finally realized that was unnecessary
and that simply offsetting the offset would work to combine them. I realized in testing that it was
possible to evade the targeting entirely, but decided to allow it as the behaviour is also more fun:
2CA-2CB 0714-0715 ▄███▄▄█▀ 73FE 29694 left targeting V3 ← V3 + 254
2CC-2CD 0716-0717 ▀▀▀ ▀█ 7301 29441 right targeting V3 ← V3 + 001
2CE-2CF 0718-0719 █▄▀ ▀▀ 5360 21344 Skip next if V3 = V6
2D0-2D1 0720-0721 ▄▄▄▀ █ 12E2 04834 Jump to integrate
2D2-2D3 0722-0723 ▀▄ ▀ 8140 33088 V1 ← V4
2D4-2D5 0724-0725 ▀▄▄▄ ▄ █ 8175 33141 V1 ← V1 − V7; VF ← borrow
2D6-2D7 0726-0727 ▀█ 6020 24608 V0 ← 032
2D8-2D9 0728-0729 ▀ ▀▀▀▀ 4F00 20224 Skip next if VF <> 000
2DA-2DB 0730-0731 ▀█ ▄ 6022 24610 V0 ← 034
2DC-2DD 0732-0733 ▄▄▄▀ █ 12E2 04834 Jump to integrate
The up and down routines combine similarly. The delay is exhausted here, as this was easiest:
2DE-2DF 0734-0735 ▄███▄█▄ 74FE 29950 up V4 ← V4 + 254
2E0-2E1 0736-0737 ▀▀▀ ▀ ▄ 7401 29697 down V4 ← V4 + 001
2E2-2E3 0738-0739 ▀▀▀▀ ▄▄█ F107 61703 integrate V1 ← delay
2E4-2E5 0740-0741 ▀▀ ▀ 3100 12544 Skip next if V1 = 000
2E6-2E7 0742-0743 ▄▄▄▀ █ 12E2 04834 Jump to integrate
The out-of-screen bounds are checked before drawing. Having two-at-a-time lines doubled the checks:
2E8-2E9 0744-0745 ▄█▄▄▄▄█▀ 43FE 17406 Skip next if V3 <> 254
2EA-2EB 0746-0747 ▄█ ▄█▀ 1336 04918 Jump to new line
2EC-2ED 0748-0749 ▄█▄▄▄█▄ 44FE 17662 Skip next if V4 <> 254
2EE-2EF 0750-0751 ▄█ ▄█▀ 1336 04918 Jump to new line
2F0-2F1 0752-0753 ▄█▄▄▄▄██ 43FF 17407 Skip next if V3 <> 255
2F2-2F3 0754-0755 ▄█ ▄█▀ 1336 04918 Jump to new line
2F4-2F5 0756-0757 ▄█▄▄▄█▄▄ 44FF 17663 Skip next if V4 <> 255
2F6-2F7 0758-0759 ▄█ ▄█▀ 1336 04918 Jump to new line
2F8-2F9 0760-0761 █ ▀█ 4341 17217 Skip next if V3 <> 065
2FA-2FB 0762-0763 ▄█ ▄█▀ 1336 04918 Jump to new line
2FC-2FD 0764-0765 ▀▄ ▀ ▄ 4421 17441 Skip next if V4 <> 033
2FE-2FF 0766-0767 ▄█ ▄█▀ 1336 04918 Jump to new line
300-301 0768-0769 █ ▀▀ 4340 17216 Skip next if V3 <> 064
302-303 0770-0771 ▄█ ▄█▀ 1336 04918 Jump to new line
304-305 0772-0773 ▀▄ ▀ 4420 17440 Skip next if V4 <> 032
306-307 0774-0775 ▄█ ▄█▀ 1336 04918 Jump to new line
That new line segment is drawn, and in-screen bounds are checked. I notice now this is unnecessary:
308-309 0776-0777 ▀█ ▀ ▀█ D341 54081 Draw 08×01 at V3,V4; VF ← XOR
30A-30B 0778-0779 ▀ ▀▀ 4300 17152 Skip next if V3 <> 000
30C-30D 0780-0781 ▄█ ▄█▀ 1336 04918 Jump to new line
30E-30F 0782-0783 ▀▄▄▄▄██ 433F 17215 Skip next if V3 <> 063
310-311 0784-0785 ▄█ ▄█▀ 1336 04918 Jump to new line
312-313 0786-0787 ▀ ▀ 4400 17408 Skip next if V4 <> 000
314-315 0788-0789 ▄█ ▄█▀ 1336 04918 Jump to new line
316-317 0790-0791 ▀ ▄▄█▄▄ 441F 17439 Skip next if V4 <> 031
318-319 0792-0793 ▄█ ▄█▀ 1336 04918 Jump to new line
This dispatch assigns the ball sprite, perhaps wastefully, and perhaps the new first line values:
31A-31B 0794-0795 ▀ █ ▄▄▀ A22C 41516 dispatch I ← ball
31C-31D 0796-0797 ▀▀ ▀ 3200 12800 Skip next if V2 = 000
31E-31F 0798-0799 ▄▀▄ ▀▀ 1328 04904 Jump to next
320-321 0800-0801 ▀ ▀▀ 8C00 35840 VC ← V0
322-323 0802-0803 ▀ ▄▄▀ 8830 34864 V8 ← V3
324-325 0804-0805 ▀▄ ▀ ▀ 8940 35136 V9 ← V4
326-327 0806-0807 ▄█▄▄▀ 123C 04668 Jump to second
Otherwise, the second line values are assigned, the earliest registers restored, and the game loops:
328-329 0808-0809 ▀ ▀▀ ▀ 8D00 36096 next VD ← V0
32A-32B 0810-0811 ▀ ▄▄▀ ▀ 8A30 35376 VA ← V3
32C-32D 0812-0813 ▀▄ ▀ ▀▀ 8B40 35648 VB ← V4
32E-32F 0814-0815 ▀▄▀ ▄ ▀▀ A348 41800 I ← from
330-331 0816-0817 ▀██▀ █ ▄ F465 62565 Load V0→V4; I ← I + 05
332-333 0818-0819 ▀ █ ▄▄▀ A22C 41516 I ← ball
334-335 0820-0821 ▀▄▄▀ 120C 04620 Jump to movement
The new line routine assigns starting positions randomly at the edges of that screen, before jumping
to dispatch; a line type may start in a position which immediately kills it, but this is a fine way:
336-337 0822-0823 ▀▀ ▄▄▄▄ C01E 49182 new line V0 ← ??? AND 030
338-339 0824-0825 ▀▀ █ C101 49409 V1 ← ??? AND 001
33A-33B 0826-0827 ▀▀▄▄▄▄██ C33F 49983 V3 ← ??? AND 063
33C-33D 0828-0829 ▀▀ ▄▄█▄▄ C41F 50207 V4 ← ??? AND 031
33E-33F 0830-0831 ▀▀ ▀ 3100 12544 Skip next if V1 = 000
340-341 0832-0833 ▀▀ ▀▀ 6300 25344 V3 ← 000
342-343 0834-0835 ▀ ▀ 4100 16640 Skip next if V1 <> 000
344-345 0836-0837 ▀▀ ▀ 6400 25600 V4 ← 000
346-347 0838-0839 █▄ █▀ 131A 04890 Jump to dispatch
The game ends with those initial register values:
348 0840 ██ 06 006 from
349 0841 █ 04 004
34A 0842 █ 02 002
34B 0843 █ 08 008
34C 0844 ██████ 3F 063
34D 0845 █████ 1F 031
34E 0846 █████ 1F 031
34F 0847 ████ 0F 015
I'm glad to have enhanced mine Enchantment game so thoroughly. It's genuinely fun, in mine eyes. I
notice minor flaws, but they're not damning; being able to occasionally evade the targeting lines is
fun, and the lines occasionally stopping before drawing the final pixel allows for extra mobilility,
when traversing the screen, which will become a chaotic mess anyway. My game could certainly become
smaller, but it's more easily modified this way, and it's still small. Ultimately, I'm pleased now.