Gameplay Design

It's been quite a while since my last post as I suspected it would be, things have been moving slowly but steadily towards getting the core playable features of Doc complete. Today's blog is going to be about the way Doc Cosmos 2 is played, the design choices that have gone (or will go) into it and the reasoning behind them. So lets start with the core mechanics.

Core Game Mechanics

As with the first game the sequel sees Doc trying to reach a goal by means of finding and using coloured keys to open coloured doors scattered across the level. Unlike the first game however Doc will have weapons to help him confront the numerous enemies that get in his way, and so the first task was to work out how to balance the game (create a game where each timeline is equally important) to work with weapons, a rifle in the new timeline and a sword in the old timeline:

  • In the first game Doc had no way of disposing of enemies and could at best trap them using the timeline switching mechanic. This meant that every screen revisited would still have enemies and would have to be crossed with care. By adding weapons Doc now has the ability to dispose of enemies in his path which means that going back and forth between keys and doors could become too easy as the path is cleared. The easiest way to overcome this is by making some enemies indestructible (spring loaded spikes, boulders etc) and by making sure that any that are killable can respawn. This way Doc will always have something in his way as he retraces his steps and will keep the game interesting.
  • By giving Doc a rifle in the new timeline, there was the danger of it becoming the timeline to stay in at all times as the weapon would feel sufficiently more powerful than a sword which would require close quarters. To overcome this, Docs rifle contains limited ammo which must be refilled by pouches found throughout the level. These pouches will respawn but on quite a long timer so as to force Doc to consider using the sword sometimes, in fact some enemies are better dispatched by the sword due to their movement patterns. Additionally when using the sword, enemies that advance toward the player will be stunned or knocked back, something the rifle will not do, giving the sword another advantage over the rifle.

Ammo pouches for refilling Docs rifle
  • In addition to the changes around the weapons, the games design continues to balance the timelines by trying to create an equal amount of situations that require switching such as revealing ladders & bridges.

Level and Maps

The plan has always been to make Doc 2 a much bigger game than the original, without the limitations of a 16Kb cartridge I am free to create a multiloading expansive game with several different unique locations:

  • The game will consist of four worlds. Each world will have its own unique graphical theme, enemies and music. 
  • Each world will consist of two exploration levels, finding keys and opening doors. And one boss battle level, a small level with just a boss to defeat in order to progress to the next world. The only exception is world 3 where instead of there being two exploration levels there will be only one preceded by something different that will remain secret for now (so there! :p)
  • Each of the exploration levels can be up to 130 screens in size (the original Doc Cosmos was 47 screens) not including differences due to timeline shifting.

Scoring and Replayability

In the first game Doc progressed through a single world with one goal in mind, escaping with the time device. In the sequel I wanted to create something that players could go back to and improve on. So a scoring system has been added that will allow players to try and better their high scores and collectables have been added to allow completionist players to reach 100%:

  • Throughout the game Doc will earn score for killing enemies and collecting items. At the end of each level bonus score is awarded for any collected tech pieces (see next point) and for the speed of completion. While there is no time limit for completing the level, the faster you do so the more bonus score you will receive. The reason for this bonus score is to discourage a player from just farming respawning enemies over and over in an effort to gain a high score. Additionally enemies will eventually give no score upon death if they have been killed several times.
  • On every level there will be several collectable tech pieces. These pieces serve to give additional score to the player and to add replayability. Some pieces will be obvious some will be out of the way and require some skills to find./reach. Each level will have a percentage displayed at the end of the level showing how many of the tech pieces were collected and for every level the highest percentage achieved will be stored and can be viewed at any time on the main title screen along with the best time taken to complete the level with that percentage.  An overall game completion percentage and time to complete will also be stored allowing players to monitor their overall progress. The hope is that this range of statistics will increase replayability considerably and possibly even encourage speed running.

One of many tech pieces scattered through the levels

  • As with the first game Doc 2 will have a lives system.  Losing a life will take you back to the last door you unlocked or the beginning of the level should you not have opened one yet. As this game has multiple levels, sending the player right back to level 1-1 when he/she loses all their lives would be a cruel thing to do, and so in Doc 2 when a player loses their lives they can always continue from the beginning of their current level, however their score will be reset to zero. Likewise when starting the game the player will be able to choose to start from the beginning of any level they have currently reached. Again this will encourage replay as the levels where the player has not 100% yet can be accessed from the title screen and replayed one at a time.

New Features

In addition to the weapons that Doc now has at his disposal, I wanted another way to make Doc 2 feel unique and give the player something extra to think about while playing. At the same time I did not want to create something that did not fit in with the games theme of time travel and so I came up with the concept of freeze and rewind for Docs device:

  • When Doc dies, if he has 3 or more bars of energy in his time device, it will automatically activate a rewind feature. The rewind feature costs 3 power but will rewind Docs position to a few seconds prior to his death without costing a life in the process. Only Docs position will rewind, enemies will not resurrect or otherwise move during this time. This will afford the player more chances to complete the level with the lives provided and encourage the proper management of the devices power.
  • At any time and in any timeline Doc can use his devices power to freeze time. For every bar of power consumed on the device time will freeze for 1 second. During this time the screen goes blue to indicate the effect and all enemies stop moving. This allows Doc to get past obstacles he might be otherwise to slow to do such as spikes, or to freeze enemies that might be causing problems in other ways.


I hope this gives an insight into the decisions that have been made for Doc 2 and the way it will feel to play. The majority of this functionality is in place now but I want to tweak and refine it over the coming months as I finish the rest of the game design. I'll be trying to finish the core code for the exploration levels this month and ironing out any bugs I can find with a view to moving onto the special world 3 level that shall remain secret for now. Who knows maybe next dev log I'll have something to reveal. Until then, cheerio! 


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The sword could be used to block bullets... Ala Ninja Spirit! :kreygasm


Oh dear, don't give me ideas like that!


Sounds great. Take my money!