Emanuele Feronato

New tile based platform engine – part 7 – trampolines

Talking about Platform game game, Actionscript 2, Flash and Game development.

After the AS3 translation of AS2 part 6, it’s time to introduce trampolines.

Just like ladders, trampolines have their rules. Here they are:

1 – A trampoline does not act like a wall, so a player can walk through it just like a cloud

2 – A trampoline should never be placed over another trampoline

3 – When you land on a trampoline, your vertical speed is inverted

How does this affect gameplay?

Just try to play and reach that unreachable platform as shown in the picture

Here it is the actionscript:

tile_size = 20;
ground_acceleration = 1;
ground_friction = 0.8;
air_acceleration = 0.5;
air_friction = 0.7;
ice_acceleration = 0.15;
ice_friction = 0.95;
treadmill_speed = 2;
max_speed = 3;
xspeed = 0;
yspeed = 0;
falling = false;
gravity = 0.5;
jump_speed = 6;
climbing = false;
climb_speed = 0.8;
level = new Array();
level[0] = [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1];
level[1] = [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1];
level[2] = [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 6, 1, 0, 0, 0, 0, 1];
level[3] = [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0, 0, 0, 0, 1];
level[4] = [1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 6, 0, 0, 0, 0, 0, 1];
level[5] = [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0, 0, 0, 0, 1];
level[6] = [1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 6, 1, 0, 0, 0, 0, 0, 1];
level[7] = [1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0, 0, 0, 0, 0, 6, 0, 0, 0, 0, 0, 0, 1];
level[8] = [1, 1, 1, 1, 0, 0, 0, 0, 0, 5, 5, 0, 0, 0, 7, 0, 0, 6, 0, 0, 0, 0, 0, 0, 1];
level[9] = [1, 1, 1, 1, 3, 3, 3, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 4, 4, 4, 4, 1, 1];
player = [5, 1];
function create_level(l) {
	_root.createEmptyMovieClip("level_container", 1);
	level_height = l.length;
	level_width = l[0].length;
	for (y=0; ymax_speed) {
		xspeed = max_speed;
	}
	if (xspeed0) {
		if ((bottom_right != 0 and bottom_right != 6) or (bottom_left != 0 and bottom_left != 6)) {
			// not a cloud...
			if (bottom_right != 5 and bottom_left != 5) {
				// a trampoline
				if ((bottom_right == 7 or bottom_left == 7) and (Math.abs(yspeed)>1)) {
					yspeed = yspeed*-1;
					jumping = true;
					falling = true;
				} else {
					y_pos = bottom*tile_size-9;
					yspeed = 0;
					falling = false;
					jumping = false;
				}
			} else {
				//cloud
				if (prev_bottom0) {
		if ((top_right != 0 and top_right != 5 and top_right != 6 and top_right != 7) or (bottom_right != 0 and bottom_right != 5 and bottom_right != 6 and bottom_right != 7)) {
			x_pos = right*tile_size-6;
			xspeed = 0;
		}
	}
	prev_bottom = bottom;
}
function get_edges() {
	// right edge
	right = Math.floor((x_pos+5)/tile_size);
	// left edge   
	left = Math.floor((x_pos-6)/tile_size);
	// bottom edge
	bottom = Math.floor((y_pos+8)/tile_size);
	// top edge
	top = Math.floor((y_pos-9)/tile_size);
	// adjacent tiles
	top_right = level[top][right];
	top_left = level[top][left];
	bottom_left = level[bottom][left];
	bottom_right = level[bottom][right];
}

And this is the result:

Download the source code and enjoy.