#Christmas Cannon Challenge

Use your Christmas Cannon to deliver gifts by shooting them into chimneys. This challenge focuses on calculating the trajectory of a projectile over time. The provided code handles rotation/aiming the cannon and chimney-gift collisions.

Challenge thread: https://www.reddit.com/r/pygame/comments/3xpi6t/challenge_christmas_cannon/

#How It Works

Run main.py to launch the game.

###Collisions

Because of the high speed of gifts, it's possible for a gift to pass through a chimney cap without a collision being detected. To handle this, a rect that covers the area between the gift's last and current positions is also checked for collision with the chimney cap.

###Controls

Mouse Position Aim Cannon

Mouse Click Shoot Gift

F Toggle Fullscreen

ESC Exit

#Challenge

Calculate the trajectory of Gift objects launched from the Christmas Cannon using the following formulas:

x = initial_x_position + (initial_x_velocity * time_elapsed)

y = initial_y_position - (initial_y_velocity * time_elapsed) - (.5 * GRAVITY * time_elapsed**2)

Note that the distance travelled on the y-axis is subtracted from the initial y-position because the screen's y-axis is inverted.

Hint: You can use angles.project to find the initial x and y velocities

Suggested values (or what I used, at least):

GRAVITY = 9.8 (this is the actual acceleration of gravity in meters/second^2, however, it is positive due to the inverted y-axis)

Cannon.firing_speed = 125

time_elapsed = time since firing in milliseconds / 100 (dividing by 100 keeps the gift from moving too fast on the screen)

#Achievements

Trigger Happy Jack Frost Implement a cooldown period after firing the cannon and restrict the cannon to firing on left-clicks only.

More (Or Less) Into the Breech, My Friend Display the cannon's firing speed attribute onscreen and allow the player to adjust it.

Gift Exchange The player should start each level with a certain number of gifts. Successfully delivering a gift to a house which hasn't received one should give the player a number of additional gifts to fire. Award the player points based on how many gifts they have left after completing the level.

Failure Is An Option Implement level failure if the player runs out of gifts before delivering a gift to each house. Add a new GameState that alerts the player of their failure and allows them to restart the level.