Make game more interesting (and 544 bytes long...)
Cat's Eye Technologies
7 years ago
| 18 | 18 | |
| 19 | 19 | reserve vector save_cinv |
| 20 | 20 | |
| 21 | // these are zero-page so that we can use them as indirect addresses | |
| 22 | // through which we write to screen memory | |
| 21 | 23 | assign word position $fb |
| 22 | 24 | assign word new_position $fd |
| 23 | 25 | |
| 26 | 28 | reserve word compare_target |
| 27 | 29 | |
| 28 | 30 | reserve word[16] actor_pos |
| 31 | reserve word[16] actor_delta | |
| 29 | 32 | |
| 30 | 33 | reserve vector dispatch_state |
| 31 | 34 | reserve vector dispatch_logic |
| 42 | 45 | sta >new_position |
| 43 | 46 | } |
| 44 | 47 | |
| 48 | // output is carry | |
| 45 | 49 | routine compare_new_pos { |
| 46 | 50 | lda >new_position |
| 47 | 51 | cmp >compare_target |
| 52 | 56 | } |
| 53 | 57 | } |
| 54 | 58 | |
| 59 | // output is carry | |
| 55 | 60 | routine check_new_position_in_bounds { |
| 56 | 61 | copy #$07e8 compare_target // just past bottom of screen |
| 57 | 62 | jsr compare_new_pos |
| 91 | 96 | } |
| 92 | 97 | } |
| 93 | 98 | |
| 94 | routine read_stick { | |
| 99 | routine read_stick outputs (delta) { | |
| 95 | 100 | lda #0 |
| 96 | 101 | sta <delta |
| 97 | 102 | sta >delta |
| 144 | 149 | asl .a |
| 145 | 150 | asl .a |
| 146 | 151 | copy .a <actor_pos, y |
| 152 | ||
| 153 | // sigh | |
| 154 | // copy #$0001 actor_delta, y | |
| 155 | copy #00 >actor_delta, y | |
| 156 | copy #40 <actor_delta, y | |
| 157 | ||
| 147 | 158 | iny |
| 148 | 159 | cpy #8 |
| 149 | 160 | } |
| 183 | 194 | } else { } |
| 184 | 195 | } |
| 185 | 196 | |
| 197 | routine reverse_delta { | |
| 198 | lda #40 | |
| 199 | cmp <delta | |
| 200 | if beq { | |
| 201 | // copy #-40 delta | |
| 202 | lda #216 | |
| 203 | sta <delta | |
| 204 | lda #255 | |
| 205 | sta >delta | |
| 206 | } else { | |
| 207 | // copy #40 delta | |
| 208 | lda #40 | |
| 209 | sta <delta | |
| 210 | lda #0 | |
| 211 | sta >delta | |
| 212 | } | |
| 213 | } | |
| 214 | ||
| 186 | 215 | routine logic_obstacle { |
| 187 | lda #0 | |
| 188 | sta >delta | |
| 189 | lda #1 | |
| 190 | sta <delta | |
| 191 | 216 | jsr calculate_new_position |
| 192 | 217 | jsr check_new_position_in_bounds |
| 193 | 218 | if bcs { |
| 198 | 223 | lda #82 |
| 199 | 224 | ldy #0 |
| 200 | 225 | sta (position), y |
| 201 | } else { } | |
| 226 | } else { | |
| 227 | jsr reverse_delta | |
| 228 | } | |
| 202 | 229 | } |
| 203 | 230 | |
| 204 | 231 | routine indirect_jsr_logic { |
| 212 | 239 | stx save_x |
| 213 | 240 | |
| 214 | 241 | copy actor_pos, x position |
| 242 | copy actor_delta, x delta | |
| 215 | 243 | |
| 216 | 244 | cpx #0 |
| 217 | 245 | if beq { |
| 223 | 251 | |
| 224 | 252 | ldx save_x |
| 225 | 253 | copy position actor_pos, x |
| 254 | copy delta actor_delta, x | |
| 226 | 255 | |
| 227 | 256 | inx |
| 228 | 257 | cpx #8 |