:root {
    --text-main: #334155;
    --text-strong: #0f172a;
    --text-muted: #5b718a;
    --panel: rgba(255, 255, 255, 0.62);
    --panel-border: rgba(255, 255, 255, 0.9);
    --accent: #2f6df3;
    --accent-soft: rgba(47, 109, 243, 0.2);
    --accent-strong: #1f5be0;
    --danger-soft: rgba(248, 113, 113, 0.18);
    --danger: #b91c1c;
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    min-height: 100vh;
    padding: 16px;
    font-family: Inter, sans-serif;
    color: var(--text-main);
    background-color: #69adff;
    background-image: linear-gradient(180deg, #8ec5ff 0%, #69adff 52%, #4b97f3 100%);
    position: relative;
    overflow-x: hidden;
}



h1,
h2,
h3 {
    margin: 0;
    font-family: Merriweather, serif;
    color: var(--text-strong);
}

.page-header {
    text-align: center;
    margin-bottom: 24px;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 14px;
    margin-top: 6px;
}

.page-header h1 {
    font-size: clamp(2rem, 5vw, 3.4rem);
    letter-spacing: -0.02em;
}

.hero-subtitle {
    margin: 0;
    font-size: clamp(1rem, 2vw, 1.2rem);
    color: var(--text-muted);
    max-width: 720px;
}

.hero-cta {
    margin-top: 4px;
    padding: 10px 20px;
    border-radius: 999px;
    background: linear-gradient(180deg, #111827, #1f2937);
    color: #f8fafc;
    font-weight: 600;
    letter-spacing: 0.01em;
    box-shadow: 0 14px 28px rgba(15, 23, 42, 0.22);
}


.panel {
    background: var(--panel);
    border: 1px solid var(--panel-border);
    border-radius: 24px;
    padding: 24px;
    box-shadow: 0 20px 42px rgba(67, 96, 128, 0.18);
    backdrop-filter: blur(20px);
    position: relative;
}

.panel::before {
    content: "";
    position: absolute;
    inset: 0;
    border-radius: inherit;
    pointer-events: none;
    background: linear-gradient(160deg, rgba(255, 255, 255, 0.58), rgba(255, 255, 255, 0.2));
}

#guide-panel {
    max-width: 1200px;
    margin: 0 auto 20px;
    overflow-x: hidden;
}

#guide-panel h2 {
    margin-bottom: 12px;
}

#guide-panel h3 {
    margin-top: 14px;
    margin-bottom: 8px;
    font-size: 1rem;
}

.guide-list {
    margin: 0;
    padding-left: 18px;
    line-height: 1.6;
    overflow-wrap: anywhere;
    word-break: break-word;
}

.guide-list li + li {
    margin-top: 6px;
}

.mono {
    font-family: "JetBrains Mono", monospace;
    color: #1d4ed8;
    display: inline-block;
    max-width: 100%;
    white-space: normal;
    overflow-wrap: anywhere;
    word-break: break-word;
}

.guide-flow {
    margin: 0;
    line-height: 1.7;
    color: var(--text-muted);
    font-size: 1.02rem;
}

.app-layout {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    gap: 20px;
}

#tape-section h2,
#rules-input h2,
#input-section h2,
#diagram-container h2 {
    margin-bottom: 14px;
}

#machine-container {
    position: relative;
    padding-bottom: 24px;
}

#tape-container {
    overflow-x: auto;
    padding-bottom: 8px;
}

#tape {
    display: flex;
    gap: 8px;
    min-height: 56px;
}

.tape-cell {
    width: 48px;
    height: 48px;
    border-radius: 12px;
    border: 1px solid #cbd5e1;
    background: rgba(255, 255, 255, 0.84);
    color: var(--text-main);
    font-family: "JetBrains Mono", monospace;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s ease;
}

.tape-cell.active {
    border-color: var(--accent);
    background: linear-gradient(180deg, rgba(47, 109, 243, 0.26), rgba(47, 109, 243, 0.14));
    color: var(--text-strong);
    box-shadow: 0 6px 20px rgba(47, 109, 243, 0.2);
}

#head-container {
    position: relative;
    height: 16px;
    margin-top: 6px;
}

#head {
    position: absolute;
    width: 0;
    height: 0;
    border-left: 12px solid transparent;
    border-right: 12px solid transparent;
    border-top: 12px solid var(--accent);
    transition: left 0.2s ease;
}

.core-grid {
    display: grid;
    grid-template-columns: 1.5fr 1fr;
    gap: 20px;
}

.left-column {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

#rules,
#input-string {
    width: 100%;
    border-radius: 14px;
    border: 1px solid #cbd5e1;
    background: rgba(255, 255, 255, 0.82);
    color: var(--text-main);
    font-family: "JetBrains Mono", monospace;
    padding: 14px;
    outline: none;
    transition: all 0.2s ease;
}

#rules {
    min-height: 220px;
    resize: vertical;
}

#rules:focus,
#input-string:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 2px var(--accent-soft);
}

#diagram-view {
    min-height: 220px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.mermaid,
.mermaid svg {
    width: 100%;
    font-family: Inter, sans-serif !important;
}

.controls-status-panel {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
    align-items: start;
}

#controls-container h3,
#status-container h3 {
    margin-bottom: 12px;
}

.button-row {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.btn {
    border-radius: 14px;
    padding: 10px 18px;
    font-family: Inter, sans-serif;
    font-weight: 600;
    border: 1px solid transparent;
    cursor: pointer;
    transition: all 0.2s ease;
}

.btn-secondary {
    background: rgba(226, 232, 240, 0.9);
    color: #0f172a;
}

.btn-secondary:hover {
    background: #cbd5e1;
}

.btn-outline {
    background: transparent;
    border-color: #94a3b8;
    color: var(--text-main);
}

.btn-outline:hover {
    background: rgba(148, 163, 184, 0.2);
}

.btn-outline-primary {
    background: transparent;
    border-color: var(--accent);
    color: var(--accent);
}

.btn-outline-primary:hover {
    background: var(--accent);
    color: #f8fafc;
}

.btn-primary {
    background: linear-gradient(180deg, #2f6df3, #1f5be0);
    color: #f8fafc;
    box-shadow: 0 12px 28px rgba(47, 109, 243, 0.34);
}

.btn-primary:hover {
    background: linear-gradient(180deg, #3a76f4, #2b66e4);
}

.btn:disabled {
    opacity: 0.65;
    cursor: not-allowed;
}

.status-row {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 10px;
}

.status-label {
    color: var(--text-muted);
    font-weight: 600;
}

.badge {
    border-radius: 999px;
    padding: 4px 10px;
    border: 1px solid #bfdbfe;
    font-family: "JetBrains Mono", monospace;
    font-size: 0.9rem;
}

.badge-state {
    background: rgba(30, 58, 138, 0.12);
    color: #1e3a8a;
    border-color: #93c5fd;
}

#guide-panel {
    margin-bottom: 22px;
}

.badge-state.halted {
    background: var(--danger-soft);
    color: var(--danger);
    border-color: #fecaca;
}

.badge-steps {
    background: rgba(147, 51, 234, 0.14);
    color: #6b21a8;
    border-color: #c4b5fd;
}

@media (max-width: 960px) {
    .core-grid,
    .controls-status-panel {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 640px) {
    body {
        padding: 12px;
    }

    .panel {
        padding: 16px;
        border-radius: 18px;
    }

    .guide-list {
        padding-left: 16px;
    }

    .button-row .btn {
        width: 100%;
    }
}