Due to PICO-8 only having 2 buttons, I've had to use the system pause key and a keyboard key for the inventory buttons. This unfortunately means that you have to use a keyboard for this.
If sitting that close together is uncomfortable (or impossible due to restrictions), you should be able to use 2 keyboards, one for each player, and sit an appropriate distance apart.

Player 1:
Z/C/N - Jump
X/V/M - Use item
Left/Right arrows - Move
Up/Down arrows - Aim tool up or down
P/Enter - Open crafting/inventory screen

Player 2:
Tab/W - Jump
Q/A - Use item
S/F - Move
E/D - Aim tool up or down
T - Open crafting/inventory screen

Inventory screen:
🅾️ - Pick up item or craft
❎ - Move selected item to trash
⬆️/⬇️ - Scroll / change selected item
⬅️ - Go to Left side
➡️(Left side) - Go to Right side
➡️(Right side) - Recover trashed item

General tips:

• Cut trees with the axe, mine blocks with the pickaxe, and attack enemies with the sword.
• To craft items, open the inventory and press left to go to the crafting column. There you can press O/Z to craft one of the highlighted item or hold it to keep crafting that item until you let go or run out of materials.
• You can drop items one at a time by picking them up from your inventory (so it "floats" to the side) and then pressing the trash key. If done incorrectly, you can recover the item from trash by pressing right.
• To change the selected item, open the inventory and press up or down, then close the inventory.
• Platforms are placed one block lower while moving horizontally to make building platform bridges easier. Just hold the use item button and walk!
• Hold down, X and left or right while holding a block to build a platform horizontally.
• Hold down, X and jump while holding a block to build vertically.

• Unsure, but mobs may be unable to spawn around player one. I'll have to check to make sure.
  

• How do I do < insert something here >?
  • Have you looked through the main post in the original version's thread? You can click this text to go there.
• Why can't I save in this version?
  • I already answered that above, but anyway, unfortunately I had to scrap that, among other things, just to get split-screen to even work.
• Why is this a separate cartridge?
  • Because there wasn't enough space in the main cart, and to my knowledge, there isn't much I can do to further optimise what's there.
• Why is the performance so bad I want a refund.
  • First of all, it was pushing the limits already with one player, a second one just makes basically everything player-related cost twice as much (and I kind of just threw it together). Second, this is a free product!