Bonus effects

In this part I want to implement four bonus effects: accelerate/decelerate the ball, and increase/decrease the platform size.

A bonus effect is applied when the player catches a falling bonus with the platform, i.e. on bonus-platform collision. So, in the first place it is necessary to detect such types of collisions.

function collisions.resolve_collisions( ball, platform,
                                        walls, bricks, bonuses )
   .....
   collisions.platform_bonuses_collision( platform, bonuses, ball )       --(*1)
end

function collisions.platform_bonuses_collision( platform, bonuses, ball )
   local overlap
   local b = { x = platform.position.x,
               y = platform.position.y,
               width = platform.width,
               height = platform.height }
   for i, bonus in pairs( bonuses.current_level_bonuses ) do
      local a = { x = bonus.position.x - bonuses.radius,
                  y = bonus.position.y - bonuses.radius,
                  width = 2 * bonuses.radius,
                  height = 2 * bonuses.radius }      
      overlap = collisions.check_rectangles_overlap( a, b )
      if overlap then
         bonuses.bonus_collected( i, bonus, ball, platform )             --(*2)
      end
   end
end

(*1): Check for bonus-platform collisions is inserted along with the other collisions checks.
(*2): A bonus-platform overlap is checked similarly to the platform-ball. If an overlap is detected, a function bonuses.bonus_collected that applies bonus effect is called.

To apply bonus effect, first it is necessary to determine the bonus type. The procedure is analogous to the bricks.

function bonuses.bonus_collected( i, bonus, ball, platform )
   if bonuses.is_slowdown( bonus ) then
      .....
   elseif bonuses.is_accelerate( bonus ) then
      .....
   elseif bonuses.is_increase( bonus ) then
      .....
   elseif bonuses.is_decrease( bonus ) then
      .....
   end
   table.remove( bonuses.current_level_bonuses, i )
end

function bonuses.is_slowdown( single_bonus )
   local col = single_bonus.bonustype % 10
   return ( col == 1 )
end

function bonuses.is_accelerate( single_bonus )
   local col = single_bonus.bonustype % 10
   return ( col == 5 )
end

function bonuses.is_increase( single_bonus )
   local col = single_bonus.bonustype % 10
   return ( col == 3 )
end

function bonuses.is_decrease( single_bonus )
   local col = single_bonus.bonustype % 10
   return ( col == 6 )
end

3. Accelerate-decelerate ball

function bonuses.bonus_collected( i, bonus, ball, platform )
   if bonuses.is_slowdown( bonus ) then
      ball.react_on_slow_down_bonus()
   elseif bonuses.is_accelerate( bonus ) then
      ball.react_on_accelerate_bonus()
   elseif 
   .....
end

function ball.react_on_slow_down_bonus()
   local slowdown = 0.7
   ball.speed = ball.speed * slowdown
end

function ball.react_on_accelerate_bonus()
   local accelerate = 1.3
   ball.speed = ball.speed * accelerate
end

4. Platfrom increase-decrease

function bonuses.bonus_collected( i, bonus, ball, platform )
   if 
      .....
   elseif bonuses.is_increase( bonus ) then
      platform.react_on_decrease_bonus()
   elseif bonuses.is_decrease( bonus ) then
      platform.react_on_increase_bonus()
   end
   table.remove( bonuses.current_level_bonuses, i )
end

...
platform.width = platform.norm_tile_width
platform.height = platform.norm_tile_height
platform.size = "norm"

function platform.react_on_decrease_bonus()
   if platform.size == "norm" then
      platform.width = platform.small_tile_width
      platform.height = platform.small_tile_height
      platform.quad = love.graphics.newQuad(
         platform.small_tile_x_pos, platform.small_tile_y_pos,
         platform.small_tile_width, platform.small_tile_height,
         platform.tileset_width, platform.tileset_height )
      platform.size = "small"
   elseif platform.size == "large" then
      platform.width = platform.norm_tile_width
      platform.height = platform.norm_tile_height
      platform.quad = love.graphics.newQuad(
         platform.norm_tile_x_pos, platform.norm_tile_y_pos,
         platform.norm_tile_width, platform.norm_tile_height,
         platform.tileset_width, platform.tileset_height )
      platform.size = "norm"     
   end
end

function platform.react_on_increase_bonus()
   if platform.size == "small" then
      platform.width = platform.norm_tile_width
      platform.height = platform.norm_tile_height
      platform.quad = love.graphics.newQuad(
         platform.norm_tile_x_pos, platform.norm_tile_y_pos,
         platform.norm_tile_width, platform.norm_tile_height,
         platform.tileset_width, platform.tileset_height )
      platform.size = "norm"
   elseif platform.size == "norm" then
      platform.width = platform.large_tile_width
      platform.height = platform.large_tile_height
      platform.quad = love.graphics.newQuad(
         platform.large_tile_x_pos, platform.large_tile_y_pos,
         platform.large_tile_width, platform.large_tile_height,
         platform.tileset_width, platform.tileset_height )
      platform.size = "large"
   end
end

5. Care should be taken regarding platform sizes if next level is reached or the ball is lost.

function game.enter( prev_state, ... )
   .....
   if args and args.current_level then
      .....
      ball.reposition()
      platform.reset_size_to_norm()
   end      
end


function game.check_no_more_balls( ball, lives_display )
   if ball.escaped_screen then
      .....
         ball.reposition()
         platform.reset_size_to_norm()
      .....
   end
end

function platform.reset_size_to_norm()
   platform.width = platform.norm_tile_width
   platform.height = platform.norm_tile_height
   platform.quad = love.graphics.newQuad(
      platform.norm_tile_x_pos, platform.norm_tile_y_pos,
      platform.norm_tile_width, platform.norm_tile_height,
      platform.tileset_width, platform.tileset_height )
   platform.size = "norm"   
end