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powerups.asm
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powerups.asm
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# MAV120
# Mathew Varughese
.data
last_powerup_frame: .word 0
POWER_UP_FRAME_TIMING: .word 60
CHANCES_POWERUP_SHOWS: .word 10 # 1 in a __ chance
powerup_x: .word 0
powerup_y: .word 52
powerup_player_has_equipped: .byte 0
current_powerup_on_screen: .byte 0
# 0: Nothing
# 1: More Ammo
# 2: Extra Life
# 3: Temp Invincible
# 4: Freeze Ships
.eqv NUM_OF_POWERUPS 5 # this is actual one more than the actual number, to simplify some code
# Array that holds the addresses of the sprites. Makes code less complex.
powerup_sprite_array: .word 0:NUM_OF_POWERUPS
# Array that has pointers to functions.
powerup_fn_array: .word 0:NUM_OF_POWERUPS
.text
set_up_powerup_sprite_array:
enter
la t0 powerup_extra_bullets_sprite
la t1 powerup_extra_life_sprite
la t2 powerup_invincibility_sprite
la t3 powerup_freeze_sprite
li t9 4
sw t0 powerup_sprite_array(t9)
li t9 8
sw t1 powerup_sprite_array(t9)
li t9 12
sw t2 powerup_sprite_array(t9)
li t9 16
sw t3 powerup_sprite_array(t9)
leave
set_up_powerup_fn_array:
enter
la t0 add_bullets_powerup
la t1 add_extra_life_powerup
la t2 add_invincibility_powerup
la t3 add_freeze_powerup
li t9 4
sw t0 powerup_fn_array(t9)
li t9 8
sw t1 powerup_fn_array(t9)
li t9 12
sw t2 powerup_fn_array(t9)
li t9 16
sw t3 powerup_fn_array(t9)
leave
check_to_add_powerup:
enter s0
# Every POWER_UP_FRAME_TIMING frames, a power up has a 1 in
# CHANCES_POWERUP_SHOWS chance to show up.
lbu t1 current_powerup_on_screen
bne t1 0 _finish_check_to_add_power_up
# the following determines difference between last powerup
# or since start of game
lw t0 last_powerup_frame
lw t1 frame_counter
beq t0 0 _load_game_start_frame_instead
b _finish_loading_frame_counter
_load_game_start_frame_instead:
lw t0 game_start_frame
_finish_loading_frame_counter:
sub t0 t1 t0
# t0 = frames since last power up
lw t9 POWER_UP_FRAME_TIMING
blt t0 t9 _finish_check_to_add_power_up
sw t1 last_powerup_frame
# a0 = random [0,CHANCES_POWERUP_SHOWS-1]
li v0 sys_randRange
lw a1 CHANCES_POWERUP_SHOWS
syscall
bne a0 0 _finish_check_to_add_power_up
jal add_powerup
lw t1 frame_counter
sw t1 last_powerup_frame
_finish_check_to_add_power_up:
leave s0
add_powerup:
enter
li v0 sys_randRange
li a1 NUM_OF_POWERUPS
syscall
sb a0 current_powerup_on_screen
# a0 = 1 # uncomment this line to force a certain powerup
lw t0 player_y
sw t0 powerup_y
lw t0 player_x
bge t0 32 _place_power_up_on_left
_place_power_up_on_right:
li t0 51
b _set_powerup_position
_place_power_up_on_left:
li t0 8
_set_powerup_position:
sw t0 powerup_x
leave
check_if_touching_powerup:
enter
lw a0 powerup_x
add a0 a0 3
lw a1 powerup_y
add a1 a1 3
lw a2 player_x
lw a3 player_y
li v0 0
jal check_if_inside_hitbox
beq v0 0 _not_touching_powerup
lbu t0 current_powerup_on_screen
sb t0 powerup_player_has_equipped
sb zero current_powerup_on_screen
lw t0 frame_counter
sw t0 last_powerup_frame
_not_touching_powerup:
leave