Dumblador turns back

Here it comes. Some final tweaks on dumblador's "walk to the right" animation last night and I now have a CompoundGob that turns back when it encounters a wall (how sweet ^_^)

Please bear some GobScript since it's still a pretty simple and straightforward monster:

anim1 = spr:0
anim2 = spr:3

statL0 :anim1 {
using walker
selfmove
test 0 (2,4)-(8,14) 0001
area 0 (0,0)-(8,4) 000A
}

statR1 :anim2 { using walker selfmove test 0 (2,4)-(8,14) 0001 area 0 (0,0)-(8,4) 000A } statL0->statR1 on fail (100 :0) statR1->statL0 on fail (100 ~ :0) statL0->statR1 on hit0 (100 :0) statR1->statL0 on hit0 (100 ~ :0) end

The only thing you have to remember about your spritesheet is now the position in the animation slots where your things are. That's slots #0 (walk left) and #3 (walk right) for me. You give them animation identifiers for your monster (1 and 2, resp.) From that, you can define states walk left and walk right. Each state defines an animation being played and a behaviour. The combination of using walker and selfmove means that DumBlador will move forward at constant speed, according to what's defined in the animation, but not faster than the value defined in its internal variable v0 (x speed)

"walker" is what's called a controller for the GOB. It can also report events and indicate when it failed to perform the desired movement. The two on fail statements indicate transitions from "walk left" to "walk right" and back when it's no longer possible to move forward. That could be due to a wall or the end of a platform. With this simple script, dumblador "has no way to figure out".

Another part of the current behaviour is that dumblador turns back when Bilou jumps on his "head". This is achieved by the two on hit statements. It's still necessary to provide the (relative) coordinates of the hitboxes manually. Here the "hit" statement corresponds to a passive area in the state definition, which is seen in dark cyan in the Inspector widget. "000A" is the bit mask that corresponds to Bilou's stomping action or AppleAssault's attacks. I could have used "0002" to make DumBlador impervious to punch attacks and reacts only to stomps.

Finally, the curious (100 ~ :0) are GobExpressions. It's a minimalist encoding of "set var[0] to -100". It works as those RPN calculators, where you type "2 40 +" to compute "40 + 2". Only simple parts are used here: push the constant 100, negate it (I don't have negative constants so far ^^") and assign it to variable 0 (mnemonic: Pascal uses := for assignments). Reusing a constant here is required as the walker controller is allowed to alter the speed in the final steps towards the wall.

Would you like to give it a try yourself ?