Now it's starting to resemble a game. Loosely.
In this step we add gravity and jumping. The player will fall if there is no blocking char below. On joystick up the player jumps in a curve.
Both fall speed and jump speed are non linear and based on tables.
This step shows:
-jumping (following a delta y curve)
Most prominent addition are the jump and fall table. These hold the deltas we use to make the movement not look linear but somewhat naturalistic:
PLAYER_JUMP_POS !byte 0 PLAYER_JUMP_TABLE !byte 8,7,5,3,2,1,1,1,0,0 PLAYER_FALL_POS !byte 0 FALL_SPEED_TABLE !byte 1,1,2,2,3,3,3,3,3,3
The jump is only possible if the player is not falling. Once the player jumped the PLAYER_JUMP_POS is increased on every frame and the player moved upwards for entry-of-jump-table pixel. If the player is blocked moving upwards the jump is aborted:
.PlayerIsJumping inc PLAYER_JUMP_POS lda PLAYER_JUMP_POS cmp #JUMP_TABLE_SIZE bne .JumpOn lda #0 sta PLAYER_JUMP_POS jmp .JumpComplete .JumpOn ldx PLAYER_JUMP_POS lda PLAYER_JUMP_TABLE,x beq .JumpComplete sta PARAM5 .JumpContinue jsr PlayerMoveUp beq .JumpBlocked dec PARAM5 bne .JumpContinue jmp .JumpComplete .JumpBlocked lda #0 sta PLAYER_JUMP_POS jmp .JumpStopped
To check for falling an attempt is made to move the player down one pixel. If he is blocked he is standing on solid ground. If he can fall the fall counter is increased. The fall counter is increased in every frame up to the max number of entries in the fall table.
If the player is falling the player is moved down entry-of-fall-table pixel.
.PlayerFell ldx PLAYER_FALL_POS lda FALL_SPEED_TABLE,x beq .FallComplete sta PARAM5 .FallLoop dec PARAM5 beq .FallComplete jsr PlayerMoveDown jmp .FallLoop .FallComplete lda PLAYER_FALL_POS cmp #( FALL_TABLE_SIZE - 1 ) beq .FallSpeedAtMax inc PLAYER_FALL_POS .FallSpeedAtMax