:root {
    --background-colour: #f8f9fa;
    --dark-text-colour: #343a40;
    --light-text-colour: #fff;
    --title-colour: #1a54b5;
    --subtitle-colour: #6c757d;
    --parameters-background-colour: #fff;
    --parameter-border-colour: #ced4da;
    --header-background-colour: #e3f2fd;
    --data-background-colour: #f1f8ff;
    --data-hover-colour: #d1e8ff;
    --button-background-colour: #007bff;
    --button-hovered-background-colour: #0069d9;
    --slider-track-colour: #007bff;
    --slider-thumb-colour: #0069d9;
    --error-background-colour: #db2b1f;
    --machine-background-colour: #fff;
    --head-border-colour: #007bff;
    --head-background-colour: #cce5ff;
    --head-text-colour: #004085;
    --tape-border-colour: #dee2e6;
    --tape-background-colour: #f8f9fa;
    --highlight-color: #ffc107;
}

body {
    font-family: "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    font-size: 1rem;
    line-height: 1.5;
    background-color: var(--background-colour);
    color: var(--dark-text-colour);
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
}

header {
    text-align: center;
    margin-bottom: 2rem;
    padding-bottom: 1.5rem;
    border-bottom: 1px solid var(--parameter-border-colour);
}

h1 {
    text-align: center;
    color: var(--title-colour);
    font-size: 2.5rem;
    margin-bottom: 1.5rem;
    font-weight: 500;
    letter-spacing: -0.5px;
}

.subtitle {
    color: var(--subtitle-colour);
    font-size: 1.1rem;
    margin-top: -1rem;
}

#parameters {
    display: grid;
    grid-template-columns: 1fr 2fr;
    gap: 15px;
    margin-bottom: 30px;
    background-color: var(--parameters-background-colour);
    padding: 25px;
    border-radius: 10px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.05);
    border: 1px solid var(--parameter-border-colour);
}

.parameter {
    padding: 10px 12px;
    border: 1px solid var(--parameter-border-colour);
    border-radius: 6px;
    font-size: 1rem;
    transition:
        border-color 0.2s,
        box-shadow 0.2s;
}

.parameter:focus {
    border-color: var(--button-background-colour);
    box-shadow: 0 0 0 3px rgba(0, 123, 255, 0.25);
}

label {
    display: flex;
    align-items: center;
    font-weight: 600;
    color: var(--dark-text-colour);
}

#state-grid {
    display: grid;
    width: 100%;
    border-collapse: collapse;
    border-radius: 10px;
    overflow: hidden;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.05);
    margin-bottom: 30px;
}

#header-row,
#subheader-row,
#headers-container,
#data-rows-container,
.state-data-row {
    display: contents;
}

.state-header,
.state-subheader,
.state-data {
    text-align: center;
    padding-top: 0.2rem;
    padding-bottom: 0.2rem;
    border: 1px solid var(--parameter-border-colour);
}

.state-header {
    grid-column: span 3;
    background-color: var(--header-background-colour);
    padding: 12px 8px;
    font-weight: 600;
    color: var(--dark-text-colour);
    border-bottom: 2px solid var(--parameter-border-colour);
}

.state-subheader {
    background-color: var(--header-background-colour);
    padding: 10px 6px;
    font-weight: 500;
    color: var(--dark-text-colour);
}

.state-data {
    background-color: var(--data-background-colour);
    padding: 10px 6px;
    transition: background-color 0.2s;
}

.state-data:hover {
    background-color: var(--data-hover-colour);
    cursor: pointer;
}

#tape-symbol-header {
    grid-row: span 2;
}

#controls {
    display: flex;
    justify-content: center;
    gap: 20px;
    margin: 30px 0;
}

.control-button {
    padding: 12px 24px;
    font-size: 1rem;
    font-weight: 500;
    background-color: var(--button-background-colour);
    color: var(--light-text-colour);
    border: none;
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.2s ease;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.control-button:hover {
    background-color: var(--button-hovered-background-colour);
    transform: translateY(-1px);
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

.control-button:active {
    transform: translateY(1px);
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.1);
}

input[type="range"] {
    -webkit-appearance: none;
    appearance: none;
    background: transparent;
    cursor: pointer;
    width: 15rem;
}

input[type="range"]::-webkit-slider-runnable-track {
    background: var(--slider-track-colour);
    height: 0.5rem;
    border-radius: 5px;
}

input[type="range"]::-moz-range-track {
    background: var(--slider-track-colour);
    height: 0.5rem;
    border-radius: 5px;
}

input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none; /* Override default look */
    appearance: none;
    margin-top: -12px; /* Centers thumb on the track */
    background-color: var(--slider-thumb-colour);
    height: 2rem;
    width: 1rem;
    border-radius: 5px;
}

input[type="range"]::-moz-range-thumb {
    border: none; /*Removes extra border that FF applies*/
    background-color: var(--slider-thumb-colour);
    height: 2rem;
    width: 1rem;
    border-radius: 5px;
}

input[type="range"]:focus {
    outline: none;
}

input[type="range"]:focus::-webkit-slider-thumb {
    border: 1px solid var(--slider-thumb-colour);
    outline: 3px solid var(--slider-thumb-colour);
    outline-offset: 0.125rem;
}

input[type="range"]:focus::-moz-range-thumb {
    border: 1px solid var(--slider-thumb-colour);
    outline: 3px solid var(--slider-thumb-colour);
    outline-offset: 0.125rem;
}

.error-message {
    border-radius: 4px;
    background-color: var(--error-background-colour);
    text-align: center;
    font-size: 1.1rem;
    color: var(--light-text-colour);
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.1);
}

#turing-machine-grid {
    display: grid;
    width: 100%;
    grid-template-rows: auto auto;
    margin-top: 40px;
    background-color: var(--machine-background-colour);
    border-radius: 10px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
    padding: 30px 15px;
}

#head-div {
    grid-row: 1;
    display: flex;
    flex-direction: column;
    border: 2px solid var(--head-border-colour);
    background-color: var(--head-background-colour);
    border-radius: 8px;
    padding: 12px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    z-index: 2;
    transform: translateY(10px);
}

#head-title {
    text-align: center;
    font-weight: bold;
    color: var(--head-text-colour);
    text-transform: uppercase;
    font-size: 0.8rem;
    letter-spacing: 1px;
    margin-bottom: 5px;
}

#state-indicator,
#position-indicator,
#step-indicator {
    text-align: center;
}

#tape-container {
    display: contents;
}

.tape {
    grid-row: 2;
    text-align: center;
    border: 1px solid var(--tape-border-colour);
    padding: 15px 10px;
    background-color: var(--tape-background-colour);
    min-height: 20px;
    font-family: monospace;
    font-size: 1.2rem;
    transition: all 0.2s ease;
}

footer {
    text-align: center;
    margin: 2rem;
}

@media (max-width: 768px) {
    body {
        padding: 15px;
    }

    h1 {
        font-size: 2rem;
    }

    #parameters {
        grid-template-columns: 1fr;
        padding: 15px;
    }

    #controls {
        flex-direction: column;
        align-items: center;
        gap: 10px;
    }

    button {
        width: 100%;
        max-width: 250px;
    }

    .tape {
        padding: 10px 5px;
        font-size: 0.9rem;
    }
}

@media (min-width: 769px) and (max-width: 1024px) {
    body {
        padding: 20px;
    }

    #turing-machine-grid {
        padding: 20px 10px;
    }
}