From 0100b052910ed3b23e5bc8ebd865e7b593c9384c Mon Sep 17 00:00:00 2001
From: RochesterX <trevorisaacmaze@gmail.com>
Date: Tue, 17 Feb 2026 22:52:47 -0500
Subject: [PATCH] Collision detection

---
 background.chr | Bin 4096 -> 4096 bytes
 plat.nes       | Bin 40976 -> 40976 bytes
 plat.s         | 371 ++++++++++++++++++++++++++++++++++++++++++++++---
 3 files changed, 348 insertions(+), 23 deletions(-)

diff --git a/background.chr b/background.chr
index b585044b670c56aa3edf02a2ee6e19f21d42d03d..9c986c5fd6b069fcca415c47810d33f2d5178e14 100644
GIT binary patch
literal 4096
zcmeH@KMKMy6vjX5;1x=7>>-?_^c0c~**r!=k5LeB(m^_Shq@>ZofM?FL}`3U+oARV
zMR;G}CExq<j~_6W={4>GLw`EwSy@vz-=)R5Hi$#t598_nvLKb__ujd^Ibx;g``DP<
zUeW5a2D0lDi<2?w;X%<z&AYSrSK}5?k(Ap+khxf)^|THu>z7s{*-9BHxR9En3bgiG
zxR5+(bfrThdbym+kULKHd@pw&mAU!x`%HidFaajO1egF5U;<2l2`~XB@E-)e1I4s#

delta 15
WcmZorXi!+dxcLI30pH{cj28ea{{`3p

diff --git a/plat.nes b/plat.nes
index 856d64015580468ea3597f3afb145e10b36e9618..8535f8d3cc58163acb577f83e9859076dfcf5683 100644
GIT binary patch
delta 1124
zcmZ`%O=uHA6rS01H=9kGW^Iygl0!$qqIj?#v;l<%iXf7Ucq!>2xfGlFb5%i_G|eO+
ztfcNm1VtiS-Kto~MGu7{RGWiPya+wTgC#vEDWwOaB)*ws{R#BV>|@^d-hA(S!<N>B
z(weZch{v84AECZ_jg<CDa)In-tr#7kJ`2$h4U<^T3~6ahL*z}K+|H3p3*_xQ6vdwy
z@A1ju=Dexs4ncPd(H&WL3i^OxdXHzTXj8P#$6bbBIE+siXN2*KR!qNA)Mtv8Pfr*1
z*<vbHMx>dqqK3=#y0X+8U(CVP4D|y3k>Q>)wgl<{utmM(lMS_u*TRvJt=y8QUhoi+
zLZ#Q#s<<IrKWM+nM2nPaW+?hKY%~P_gsEuL9;%rARWv$4R7xTR@{W=;jh|is-wjoo
zs&15I7`xxvpl(ZEcXuP1x{afbiHV1KZCYJky;&%W<W7Eh^=eUflGSU>&n(w#zRk~N
zboW9*wS1(v^g1uSQLMahoW&XF5ipgdKn-n5(H$v1LbbH0&2|=5O}Cbo?eIBg>-2?5
z4?R%8;H}r)D-x&#wM&6|AyC7OSE*j!xn5ql2fP{HsfT!QgEK>Cn7fDhWtaIMSxlup
zfHS@gjidt<51OhiSpmt4g)-D*Yqps?!nm&gna2wUGY3r-{!B*BR4bqw$p3O%Db#Bi
zA=u}*7o1MVpFE%vLN1nt%^i;s<{<<7WLboau_i{0m>4u>;kzdu)9iYvVMi=D`b5bo
zyNpxf@R&ak9KwDrg0L1qAsj)$Fh-&95S$pM@lIieLDm6=*lkp)iI;Cxl&pje-+eXn
zD~izkmtExe&~DE?{@(7fy`LT6+x{LupiC^8oSaHPP-BK#LbDm(VzHB1Vrnv(jAal{
t0+`qeH=9BW@g&3uR>!s3TcFWI*LVRqyMSjILDx7TxC)kH-lx8j?>Aceg!=#h

delta 432
zcmaiuy-UMT6vf|7+P*elO_!1m!mBu#$w?3et<=Gxo9=cg>VM!Ot!bWvAVlBbq(e%C
zbP_UjD%L?woI2UHF49GagHQy;q$r4shs))j-#x>zdYskcu1;XSPtQ?eG$hs=nQ4;O
zhFhXps=A04$g<%Sv|Wg<eUoe(B;O>RgD6tDU_Q*jn2liyFw1jA(AfgFvRJL!h+LZi
z3Nwz9X;7t7HylN;Qzhc3F_&y`c`8NllPcuw2Ys*`ZhF%<E~U|-L>^)+I9dQ<!hNT5
z1gPc|bO=x%J91n}c0{cvQ!((ZbktRLeJZ-?Tk+easptq=O`-y;^5ycDsnv4r?xSfZ
z$*S4z-qB-By7%$kX^)0#e_*4d^~0R2lD|=Z5)G*L%rC(j`Xz{j0L3%W#Q*yTU{AQj
pM4V?~N?}Dj%XF-<mz1336Uh{K9lWvUg?Ip-&`3cm#Mzc=sb2tYiHQIJ

diff --git a/plat.s b/plat.s
index dbe3be4..d7c7e5a 100644
--- a/plat.s
+++ b/plat.s
@@ -327,25 +327,40 @@ gamepad_poll:
 .segment "RODATA"
 
 level:
-.byte 0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1
-.byte 0,1,0,0,1,0,0,0,0,0,0,0,1,1,1,1
-.byte 0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1
-.byte 0,1,0,0,1,0,0,0,0,0,0,0,1,1,1,1
-.byte 0,0,1,1,0,0,0,0,0,0,0,0,0,0,0,0
 .byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
+.byte 0,1,0,0,1,0,0,0,0,1,0,0,2,7,7,3
+.byte 0,0,0,0,0,0,0,0,0,1,0,0,6,0,0,9
+.byte 0,1,0,0,1,0,0,0,0,1,0,0,6,0,0,9
+.byte 0,0,1,1,0,0,0,0,0,1,0,0,4,8,8,5
+.byte 0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0
 .byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
 .byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
 .byte 0,0,0,0,1,1,1,1,1,0,0,0,0,0,0,0
+.byte 0,0,0,0,0,0,0,0,0,0,1,0,1,0,1,0
+.byte 0,0,0,0,0,0,0,0,0,0,0,1,0,1,0,0
+.byte 0,0,0,0,0,0,0,0,0,0,1,0,1,0,1,0
+.byte 0,0,1,0,0,0,0,1,0,0,0,1,0,1,0,0
+.byte 0,1,2,3,4,5,6,7,8,9,0,0,0,0,0,0
 .byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
-.byte 0,0,0,0,0,0,0,0,1,0,1,0,1,0,0,0
-.byte 0,0,0,0,0,0,0,0,0,1,0,1,0,0,0,0
-.byte 0,0,0,0,0,0,0,0,1,0,1,0,1,0,0,0
-.byte 0,0,0,0,0,0,0,0,0,1,0,1,0,0,0,0
-.byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
+
+block_x: .res 1
+block_y: .res 1
+block_w: .res 1
+block_h: .res 1
 
 metatiles:
 .byte 0,0,0,0,0
-.byte 3,4,5,6,1
+.byte $14,$15,$16,$17,1 ; Full block
+.byte $14,$18,$1B,$0,1 ; up / left
+.byte $18,$15,$0,$19,1 ; up / right
+.byte $1B,$0,$16,$1A,1 ; down / left
+.byte $0,$19,$1A,$17,1 ; down / right
+.byte $1B,$0,$1B,$0,1 ; left
+.byte $18,$18,$0,$0,1 ; up
+.byte $0,$0,$1A,$1A,1 ; down
+.byte $0,$19,$0,$19,1 ; right
+.byte 3,3,3,3,0
+.byte 3,4,5,6,0
 
 example_palette:
 .byte $0F,$00,$3D,$20 ; greyscale
@@ -385,6 +400,7 @@ var_p:    .res 1
 jump_pressed_last_frame: .res 1
 
 frame_counter: .res 1
+last_frame_jumped: .res 1
 
 .segment "CODE"
 main:
@@ -405,6 +421,7 @@ main:
 
     lda #0
     sta frame_counter
+    sta last_frame_jumped
 
     jsr init_objects
 @loop:
@@ -526,6 +543,14 @@ init_objects:
     sta player_vel_y
     sta player_status
 
+    lda #64
+    sta block_x
+    sta block_y
+
+    lda #16
+    sta block_w
+    sta block_h
+
     rts
 
 draw:
@@ -554,7 +579,7 @@ movement:
     cmp #0
     beq :+
         ldx #1
-        lda #3
+        lda #2
         sta player_vel_x
 
         lda player_status
@@ -566,7 +591,7 @@ movement:
     cmp #0
     beq :+
         ldx #1
-        lda #253
+        lda #254
         sta player_vel_x
 
         lda player_status
@@ -607,9 +632,12 @@ movement:
     beq @fail_jump ; If jump last frame, forget it
 
     ; Jump newly pressed this frame
-    lda #250
+    lda #249
     sta player_vel_y
 
+    lda frame_counter
+    sta last_frame_jumped
+
     @fail_jump:
     
     jsr btn_a
@@ -618,7 +646,9 @@ movement:
 
     ; Gravity
     lda frame_counter
-    and #1
+    sec
+    sbc last_frame_jumped
+    and #%00000001
     cmp #0
     bne :+
         lda player_vel_y
@@ -633,6 +663,31 @@ movement:
     adc player_vel_y
     sta player_pos_y
 
+    ; Apply X velocity
+    lda player_pos_x
+    clc
+    adc player_vel_x
+    sta player_pos_x
+
+    ; load x pos, filter blocks, check up and down
+    
+    lda player_vel_y
+    cmp #0
+    bmi :+ ; branch if moving up
+        jsr downward_collision_check
+        jsr left_collision_check
+        jsr right_collision_check
+        jsr upward_collision_check
+        jmp :++
+    :
+        jsr upward_collision_check
+        jsr left_collision_check
+        jsr right_collision_check
+        jsr downward_collision_check
+    :
+
+    rts
+
     ; Keep grounded
     cmp #200
     bcc :+
@@ -641,7 +696,6 @@ movement:
         lda #200
         sta player_pos_y
     :
-
     ; Bonk
     lda #8
     cmp player_pos_y
@@ -652,13 +706,6 @@ movement:
         sta player_pos_y
     :
 
-    ; Apply X velocity
-    lda player_pos_x
-    clc
-    adc player_vel_x
-    sta player_pos_x
-
-
     rts
 
 update_background:
@@ -1012,3 +1059,281 @@ btn_a:
     lsr
     rts
 
+downward_collision_check:
+    lda #0
+    sta var_n
+    @begin_check:
+    lda player_pos_x
+    ldx var_n
+    cpx #0
+    bne :+
+        sec
+        sbc #6
+        jmp :++
+    :
+        clc
+        adc #5
+    :
+    ; divide by 16
+    clc
+    ror
+    clc
+    ror
+    clc
+    ror
+    clc
+    ror
+    sta temp_x
+
+    lda player_pos_y
+    ; divide by 16
+    clc
+    adc #8
+    clc
+    ror
+    clc
+    ror
+    clc
+    ror
+    clc
+    ror
+    tay
+
+    lda #16
+    jsr mul_y
+    adc temp_x
+    tax
+    lda level, X
+    cmp #0
+    beq :+
+        tya
+        asl
+        asl
+        asl
+        asl
+        sec
+        sbc #8
+        cmp player_pos_y
+        bcs :+
+        sta player_pos_y
+        lda #0
+        sta player_vel_y
+    :
+
+    ldx var_n
+    inx
+    stx var_n
+    cpx #1
+    beq @begin_check
+
+    rts
+
+upward_collision_check:
+    lda #0
+    sta var_n
+    @begin_check:
+    lda player_pos_x
+    ldx var_n
+    cpx #0
+    bne :+
+        sec
+        sbc #6
+        jmp :++
+    :
+        clc
+        adc #5
+    :
+    ; divide by 16
+    clc
+    ror
+    clc
+    ror
+    clc
+    ror
+    clc
+    ror
+    sta temp_x
+
+    lda player_pos_y
+    ; divide by 16
+    sec
+    sbc #8
+    clc
+    ror
+    clc
+    ror
+    clc
+    ror
+    clc
+    ror
+    tay
+
+    lda #16
+    jsr mul_y
+    adc temp_x
+    tax
+    lda level, X
+    cmp #0
+    beq :+
+        iny
+        tya
+        asl
+        asl
+        asl
+        asl
+        clc
+        adc #8
+        cmp player_pos_y
+        bcc :+
+        sta player_pos_y
+        lda #0
+        sta player_vel_y
+    :
+
+    ldx var_n
+    inx
+    stx var_n
+    cpx #1
+    beq @begin_check
+
+    rts
+
+right_collision_check:
+    lda #0
+    sta var_n
+    @begin_check:
+    lda player_pos_x
+    ; divide by 16
+    clc
+    adc #8
+    clc
+    ror
+    clc
+    ror
+    clc
+    ror
+    clc
+    ror
+    sta temp_x
+
+    lda player_pos_y
+    ldx var_n
+    cpx #0
+    bne :+
+        sec
+        sbc #7
+        jmp :++
+    :
+        clc
+        adc #6
+    :
+    ; divide by 16
+    clc
+    ror
+    clc
+    ror
+    clc
+    ror
+    clc
+    ror
+    tay
+
+    lda #16
+    jsr mul_y
+    adc temp_x
+    tax
+    lda level, X
+    cmp #0
+    beq :+
+        lda temp_x
+        asl
+        asl
+        asl
+        asl
+        sec
+        sbc #8
+        cmp player_pos_x
+        bcs :+
+        sta player_pos_x
+        lda #0
+        sta player_vel_x
+    :
+
+    ldx var_n
+    inx
+    stx var_n
+    cpx #1
+    beq @begin_check
+
+    rts
+
+left_collision_check:
+    lda #0
+    sta var_n
+    @begin_check:
+    lda player_pos_x
+    ; divide by 16
+    sec
+    sbc #8
+    clc
+    ror
+    clc
+    ror
+    clc
+    ror
+    clc
+    ror
+    sta temp_x
+
+    lda player_pos_y
+    ldx var_n
+    cpx #0
+    bne :+
+        sec
+        sbc #7
+        jmp :++
+    :
+        clc
+        adc #6
+    :
+    ; divide by 16
+    clc
+    ror
+    clc
+    ror
+    clc
+    ror
+    clc
+    ror
+    tay
+
+    lda #16
+    jsr mul_y
+    adc temp_x
+    tax
+    lda level, X
+    cmp #0
+    beq :+
+        lda temp_x
+        clc
+        adc #1
+        asl
+        asl
+        asl
+        asl
+        clc
+        adc #8
+        cmp player_pos_x
+        bcc :+
+        sta player_pos_x
+        lda #0
+        sta player_vel_x
+    :
+
+    ldx var_n
+    inx
+    stx var_n
+    cpx #1
+    beq @begin_check
+
+    rts