Dart-07 (PICO-8)

A scrolling shooter, built with PICO-8

This is a PICO-8 game, which I made during Basic Shmup Showcase event organised by Lazy Devs Academy.

You can play it here and on https://www.lexaloffle.com/bbs/?tid=49480

If you want to take a look at the codebase, please visit https://github.com/beetrootpaul/dart-07 (the code inside PICO-8 carts of this game is minified, therefore not suitable for reading).

Controls

Keyboard:

• press & hold x to fire
• press c to trigger a shockwave (if available)
• press p to open the pause menu

Virtual controller (in browser, on a mobile device):

• press & hold ❎ to fire
• press 🅾️ to trigger a shockwave (if available)
• press ➖ to open the pause menu

Physical game controllers are supposed to work as well, even in a browser. Button mapping varies between models.

Gameplay

Your task is to pilot Dart-07 unit on a secret mission on Emerald Islands.

Destroy enemies along the way to increase your score, grab power-ups left by them and survive a boss fight in order to complete a mission.

Power-ups

There are 5 types of power-ups you can grab, each of them either makes your life easier or, if cannot improve further, increases your score:

•  +1 heart – you can have max 10 hearts; you lose one whenever you take damage
•  fast movement – increases player's movement speed; does not accumulate; lost on a damage
•  fast shoot – increases shooting speed; does not accumulate, but can be combined with the triple shoot; lost on a damage
•  triple shoot – you shoot 3 bullets instead of 1, but on a little but slower rate; does not accumulate, but can be combined with the fast shoot; lost on a damage
•  shockwave charge – allows you to trigger a destructive shockwave around you (with use of "c" / "🅾️" button); you can have max 4 shockwave charges

HUD

In your HUD you see:

• left-top: mission progression (the higher the ship's icon is placed, the close to the boss you are)
• right-top: your score, which you gain by destroying enemies and grabbing power-ups in case they cannot bring any improvement
• right-middle: power-ups you gathered (excluding hearts and shockwave charges)
• left-bottom: hearts left; you die when all hearts are gone
• right-bottom: shockwave charges left; you can trigger a shockwave if you have at least 1 charge left
• top-middle, during boss fight: boss' health (yes, you are supposed to bring it down to zero 😉)

Technical Challenges Tackled In This Game

In this game I focused on learning various bits of PICO-8 API.

Some of the topics I tackled in this game are:

• multi-cart setup: this game consists of many carts – 1 main cart for the title screen etc., and 1 cart for each mission (the game contains only a single mission, but the code architecture is ready to have more of them). Each mission has its own sprites and music, as well as a code responsible for available enemy types, including their attack and movement patterns. Common SFXs and sprites are copied from the main cart to missions carts with use of MEMCPY and a user data memory area (0x4300-0x55ff), preserved across loaded carts). Moreover, I implemented this in a way which allows me to use same codebase to load both locally developed carts as well as those published to Lexaloffle BBS.
• missions defined as a map – level shape and enemy pattern are defined as sprites in a PICO-8 map, but in a
  simplified form (in order to fit all needed data there). Dedicated piece of code is responsible for translating sprites from map into a mission gameplay, including proper placement of edge land/structure tiles.
• circular clipping: during shockwave a ring of inverted colors propagates from the player. To achieve that I had to learn how to implement circular clipping masks in a CPU-performant way.
• dithered fade-in/out transition: basically a set of rectangles filled with FILLP patterns, moving over screen.
• high score: usage of PICO-8's API to read and store data persisted on a host machine
• code minification: with my code style (full of spaces and long names), I found it easy to hit PICO-8's characters' count limit. Therefore I forked and modified luamin tool and incorporated it into this game's build flow, resulting with characters' count reduced by around 50%.

Credits

I implemented this game on my own, as well as drew all sprites and composed all SFXs and music. But there are some resources I found super useful and used some of them I used in the codebase as well. With huge thanks, here are those:

• #easingcheatsheet cart by ValerADHD with copy-paste ready easing functions. See: https://www.lexaloffle.com/bbs/?tid=40577
• Circular Clipping Masks tutorial by Krystman
• Lua minification tool luamin by Mathias Bynens
• Pico-8 Music Tutorials by Gruber

Version History

v0.4.0

• Mission selection screen is now hidden in order to not expose an unfinished work

v0.3.0

• added score is shown in place of destroyed enemy and picked powerup (in case it won't have any other effect)
• increase shooting speed for a combination of triple shoot and fast shoot powerups (to make it easier to notice the change in the speed)
• increase screen shake player on damage to make it easier to realized the damage happened; remove screen shake on shockwave trigger
• fix ship sprite on the mission selection screen
• HTML5: place PICO-8 game controls closer to the game itself in order to allow narrower iframe size

v0.2.0

• new powerup type: fast movement
• fixed diagonal speed of a player's ship by dividing it by 1.41
• fast movement, fast shoot, and triple shoot have their status visible in a HUD
• more health for mission 1 boss and mission 1 big enemy
• shake camera on a shockwave trigger
• lower volume of player shooting
• show a win screen after first mission (the completed one)
• print version number on a title screen

v0.1.0

• complete game mechanics
• complete mission 1
• complete screens outside missions (but without music for a win screen after mission 3)
• implemented persisted high score