Kardinal Kid by J Bizzel is a puzzle strategy game made for ZX Spectrum. This game is quite different, but mostly inspired by “Numbertron”.
The goal of this game, as explained by the author: “You need to move a little dog around in a ‘maze’ of numbers. If you play with hearts or diamonds switched on, then you need to jump over these objects to progress. Each level has a number of objects you must jump in order to get to the next level. After you have jumped to the required amount, you can allow yourself to die to move to the next level. Hearts mode alone will be more of a challenge. You can make the game easier by playing with diamonds. Or there is a casual mode with both hearts and diamonds turned off. Toggle the options and explore so which game mode suites you.”