In this post, we will modify the block data structure to support remove left/right walls from the block. It will add more challenge to the game. What we need to do to support this feature.
– modify the function for creating block data.
– modify the function for drawing block.
– modify the function for checking collision between the player’s character and the block.
– add a condition for checking when the player’s character runs outside the block. It should start appling gravity.

It needs to have 2 boolean variables for left/right walls. If the value is false then it means no wall for that side.

function create_block(x,y,w,h,left_wall,right_wall)
   return {x=x,y=y,w=w,h=h,obstacles={},left_wall=left_wall,right_wall=right_wall}
end

Currently, we draw the block using “rect()” function. This function uses for drawing a rectangle on the screen. It doesn’t work for drawing some parts of the rectangle. we will use “line()” for drawing each side of the block instead.

function draw_block(b,c)
   if (b == nil) return

   line(b.x,b.y,b.x+b.w,b.y,c)
   line(b.x,b.y-b.h,b.x+b.w,b.y-b.h,c)

   if b.left_wall == true then
      line(b.x,b.y,b.x,b.y-b.h,c)
   end
   if b.right_wall == true then
      line(b.x+b.w,b.y,b.x+b.w,b.y-b.h,c)
   end
   
   for obs in all(b.obstacles) do
      print("✽", b.x + (b.w*obs.value), b.y - 6, 8)
   end
end

We need to add conditions in the “player_running()” function to make it support block with no left/right walls. When the player’s character hit the wall. It will use the current running direction and status of wall/no wall from block data to decide that it should hit the wall or not.

function player_running()
   local next_px = player.x + player.di
   if is_inside_block(player.x, player.y, current_block) == true and 
      is_inside_block(next_px, player.y, current_block) == false then

      if player.di == 1 and current_block.right_wall == false then

      elseif player.di == -1 and current_block.left_wall == false then

      else
         player.di = player.di * -1
         next_px = player.x + player.di
      end
   end

   player.x = next_px
end

Currently, The code starts applying gravity when the player’s character jump. If it runs outside the block without jumping. It will keep running without falling. It can fix by adding a condition to check that if the player’s character runs outside the block. It will stop staying on the ground.

function player_apply_gravity()
   local next_py = player.y
   if player.ground == false then
      
      if player.jump_counter <= 0 then
         next_py += 1
         if  is_inside_block(player.x, player.y, current_block) == true and 
            is_inside_block(player.x, next_py, current_block) == false then

            next_py = player.y
            player.ground = true
         end
      end
   else
      if is_inside_block(player.x, player.y, current_block) == false then
         player.ground = false
      end
   end

   player.y = next_py
end

player = {x=64,y=64,di=1,jump_counter=0,ground=true}

current_block = nil
block_list = {}

function create_block(x,y,w,h,left_wall,right_wall)
   return {x=x,y=y,w=w,h=h,obstacles={},left_wall=left_wall,right_wall=right_wall}
end

function draw_block(b,c)
   if (b == nil) return

   line(b.x,b.y,b.x+b.w,b.y,c)
   line(b.x,b.y-b.h,b.x+b.w,b.y-b.h,c)

   if b.left_wall == true then
      line(b.x,b.y,b.x,b.y-b.h,c)
   end
   if b.right_wall == true then
      line(b.x+b.w,b.y,b.x+b.w,b.y-b.h,c)
   end
   
   for obs in all(b.obstacles) do
      print("✽", b.x + (b.w*obs.value), b.y - 6, 8)
   end
end

function distance(x1,y1,x2,y2)
   local dx = x1-x2
   local dy = y1-y2
   local distance = sqrt(dx*dx+dy*dy)

   return distance
end

function change_current_block(b)
   
   current_block = b

   local d = distance(camera_data.target_x + 64, camera_data.target_y + 64, current_block.x + current_block.w/2, current_block.y - current_block.h/2)
   _debug = d
   if d > 12 then
      set_camera_target(current_block)
   end
end

function add_obstacle(b,v)
   if (b == nil) return
   add(b.obstacles, {value=v})
end

function is_inside_block(x,y,b)

   if (b == nil) return

   if x >= b.x and x < b.x + b.w then

      if y <= b.y and y > b.y - b.h then
          return true
      end
   end
   return false 
end

function player_running()
   local next_px = player.x + player.di
   if is_inside_block(player.x, player.y, current_block) == true and 
      is_inside_block(next_px, player.y, current_block) == false then

      if player.di == 1 and current_block.right_wall == false then

      elseif player.di == -1 and current_block.left_wall == false then

      else
         player.di = player.di * -1
         next_px = player.x + player.di
      end
   end

   player.x = next_px
end

function player_jumping()
   if btnp(4) then
      if player.jump_counter == 0 and player.ground == true then
         player.jump_counter = 20
         player.ground = false
      end
   end

   local next_py = player.y
   if player.jump_counter > 0 then
      player.jump_counter -= 1

      if player.jump_counter > 10 then
         next_py = player.y - 1  
      else
         next_py = player.y
      end
   end
   player.y = next_py
end

function player_apply_gravity()
   local next_py = player.y
   if player.ground == false then
      
      if player.jump_counter <= 0 then
         next_py += 1
         if  is_inside_block(player.x, player.y, current_block) == true and 
            is_inside_block(player.x, next_py, current_block) == false then

            next_py = player.y
            player.ground = true
         end
      end
   else
      if is_inside_block(player.x, player.y, current_block) == false then
         player.ground = false
      end
   end

   player.y = next_py
end


function player_find_new_current_block()
   if player.ground == false and 
      is_inside_block(player.x, player.y, current_block) == false then

      for b in all(block_list) do
         if is_inside_block(player.x, player.y, b) == true then
            change_current_block(b)
            break
         end
      end
   end
end

function player_hit_obstacle(b)
   if b == nil then return false end
   if is_inside_block(player.x, player.y, current_block) == false  then return false end

   for o in all(b.obstacles) do
      local d = distance(player.x, player.y, (b.x + b.w * o.value), b.y)

      if d < 3 then
         return true
      end
   end
end

function player_reset()
   player = {x=64,y=64,di=1,jump_counter=0,ground=true}
   change_current_block(block_list[1])
end

camera_data = {x=0,y=0,target_x=0,target_y=0}

function set_camera_target(b)
   if b == nil then return end

   local block_center_x = b.x + b.w/2
   local block_center_y = b.y - b.h/2

   camera_data.target_x = block_center_x - 64
   camera_data.target_y = block_center_y - 64
end

function update_camera()
   if camera_data.x > camera_data.target_x then
      camera_data.x -= 1
   elseif camera_data.x < camera_data.target_x then
      camera_data.x += 1
   end

   if camera_data.y > camera_data.target_y then
      camera_data.y -= 1
   elseif camera_data.y < camera_data.target_y then
      camera_data.y += 1
   end

   camera(camera_data.x, camera_data.y)
end

function _init()
   add(block_list, create_block(16,64,96,8,true,true))
   add(block_list, create_block(16,56,96,8,true,false))
   add(block_list, create_block(16,48,96,8,false,false))
   add(block_list, create_block(16,40,96,8,true,true))
   add(block_list, create_block(16,32,96,8,false,true))
   player_reset()

   add_obstacle(block_list[2], 0.8)
   add_obstacle(block_list[3], 0.2)
   add_obstacle(block_list[3], 0.5)
   add_obstacle(block_list[5], 0.7)

end

function _update60()
   player_running()
   player_jumping()
   player_apply_gravity()
   player_find_new_current_block()
   local hit_result = player_hit_obstacle(current_block)
   if hit_result == true then
      player_reset()
   end

   update_camera()
end

function _draw()
   cls(0)
   print("웃", player.x-3, player.y - 5, 7)
   
   for b in all(block_list) do
     draw_block(b, 7)
   end

end