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The monocore capacitor is for positive feedback for fast switching between the two motors and to slow down and avoid high frequency oscillations.

R2 together with C2 limits the maximum frequency of the monocore and motor drivers when the light is bright and the sensors are equally lit

R3 together with C2 sets the minimum frequency of the waggle even in the complete dark which is more interesting than twirling endlessly in a circle.

Having said that, maxibug is not perfect: it churns its wheels while feeding and does not back out of the feeding station when full. CD MaxiBug v5 uses just a few more parts but has powerful and efficient motor drivers, its motors are off while feeding, and it backs up when full.

The CD Maxibug v5 uses just one 74AC240 chip

By default at power-up, the circuit is in coast mode. To brake, set IN A to 0 V, IN B to 0 V, and Q5 to 5 V. To spin clockwise, set IN A to 5 V, IN B to 0 V, and Q5 to 5 V. To spin counterclockwise, set IN A to 0 V, IN B to 5 V, and Q5 to 5 V. At any time you can return to coast by applying 0 V to Q5. Or, you can apply pulses of 0 V/5 V/0 V/5 V (and so on) to control the speed. The more time spent at 5 V, the faster the motor will spin. Whenever you change modes, if you set Q5 to 0 V before making changes to IN A and IN B (and then set Q5 back to 5 V or pulsing) there will be no shoot-through.

When light shines on the LDR, it has low resistance and allows current to flow.  When light does not shine on it, the LDR has a very high resistance, and a much smaller current will not flow through it.

three-layer systems.

if a robot needs to plan ahead, it does so in a network of behaviors which talk to each other and send information around, rather than a single planner, as with hybrid systems.

Deliberative Control: Think hard, then act. Reactive Control: Don't think, (re)act. Hybrid Control: Think and act independently, in parallel. Behavior-Based Control: Think the way you act.

Li-ion batteries have the same high energy capacity as NiMHs, power output rates of NiCads, and weigh about 20%-35% less. They also have zero memory effect problems, meaning you can recharge whenever

NiCad (Nickel Cadmium) batteries are good for small to medium size range robots. They have the highest current output, are more affordable than NiMH's, and can be recharged within one or two hours

A NiCad, over many charges, can only store less and less energy after each recharge. To prevent memory effect, whenever you wish to recharge your NiCad, you must first fully discharge it.

NiCad batteries contain toxic cadmium stuff, so save a squirrel and recycle/dispose of it properly.

NiMH battaries can last many more cycles than your typical NiCad battery.

they have good current output, and have the highest energy capacity. I would recommend them for small size robots and for powering circuits. Note, NiMH batteries usually take like 10 hours to recharge depending on various factors.