diff options
Diffstat (limited to 'src/enemies.s')
| -rw-r--r-- | src/enemies.s | 36 |
1 files changed, 21 insertions, 15 deletions
diff --git a/src/enemies.s b/src/enemies.s index 25f041b..f69e9fd 100644 --- a/src/enemies.s +++ b/src/enemies.s @@ -957,22 +957,28 @@ ;; We are done going up and down. Now it's time to change the state of ;; this enemy, and home towards the player depending on its position. @start_homing: - ;; Ensure the 'state' bit is set. - tya - ora #$02 - sta Enemies::zp_enemies_pool_base + 3, x - - lda Enemies::zp_enemies_pool_base + 1, x - cmp Player::zp_screen_y - bcc @home_down - ;; TODO: up - nop - @home_down: - ;; TODO: subtract the same portion over and over. If overflow is set, then - ;; we know we are passed it. - ;; TODO: down + ;; Out of simplicity, the movement kind is picked at random. Hence, + ;; initialize the 'a' register with a random number. + stx Globals::zp_tmp0 + jsr Prng::random_valid_y_coordinate + ldx Globals::zp_tmp0 - @end: + ;; Ensure the 'state' bit is set whenever we enter back at the 'homing' + ;; function, so we can jump right into 'basic'. The 'downwards' bit is + ;; set in the next step, so zero it out for now. And set the timer to + ;; '1'. + ora #$12 + and #%00011110 + + ;; Compare the current Y position to that of the player. Then set the + ;; 'downwards' bit if it needs to go down. + ldy Enemies::zp_enemies_pool_base + 1, x + cpy Player::zp_screen_y + bcs @set_homing_to_basic + ora #$01 + + @set_homing_to_basic: + sta Enemies::zp_enemies_pool_base + 3, x rts .endproc |