:root {
    --bg-color: #0f172a;
    --panel-bg: rgba(30, 41, 59, 0.7);
    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    --primary: #3b82f6;
    --primary-hover: #2563eb;
    --secondary: #8b5cf6;
    --secondary-hover: #7c3aed;
    --border: rgba(255, 255, 255, 0.1);
    --input-bg: rgba(15, 23, 42, 0.6);
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background: linear-gradient(135deg, var(--bg-color), #020617);
    color: var(--text-main);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    padding: 2rem;
}

.app-container {
    width: 100%;
    max-width: 650px;
    animation: fadeIn 0.8s cubic-bezier(0.16, 1, 0.3, 1);
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(30px); }
    to { opacity: 1; transform: translateY(0); }
}

header {
    text-align: center;
    margin-bottom: 2.5rem;
}

.logo-icon {
    display: inline-flex;
    justify-content: center;
    align-items: center;
    width: 72px;
    height: 72px;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    border-radius: 20px;
    margin-bottom: 1.5rem;
    box-shadow: 0 15px 35px rgba(59, 130, 246, 0.3);
    transition: transform 0.3s ease;
}

.logo-icon:hover {
    transform: scale(1.05) rotate(-5deg);
}

.logo-icon svg {
    color: white;
}

header h1 {
    font-size: 2.2rem;
    font-weight: 700;
    margin-bottom: 0.75rem;
    background: linear-gradient(to right, #93c5fd, #c4b5fd);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
    letter-spacing: -0.02em;
}

header p {
    color: var(--text-muted);
    font-size: 1.05rem;
    line-height: 1.5;
}

.glass-panel {
    background: var(--panel-bg);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1px solid var(--border);
    border-radius: 28px;
    padding: 2.5rem;
    box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5), 0 inset 2px 2px rgba(255,255,255,0.05);
}

.input-group, .output-group {
    display: flex;
    flex-direction: column;
    margin-bottom: 1.75rem;
}

label {
    font-size: 0.85rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--text-muted);
    margin-bottom: 0.75rem;
}

textarea, input[type="number"] {
    width: 100%;
    background: var(--input-bg);
    border: 1px solid var(--border);
    border-radius: 16px;
    color: var(--text-main);
    font-family: inherit;
    padding: 1.25rem;
    font-size: 1rem;
    line-height: 1.5;
    transition: all 0.3s cubic-bezier(0.16, 1, 0.3, 1);
    resize: none;
}

textarea:focus, input[type="number"]:focus {
    outline: none;
    border-color: rgba(59, 130, 246, 0.5);
    background: rgba(15, 23, 42, 0.9);
    box-shadow: 0 0 0 4px rgba(59, 130, 246, 0.15);
}

textarea {
    height: 140px;
}

/* Scrollbar for textarea */
textarea::-webkit-scrollbar {
    width: 8px;
}
textarea::-webkit-scrollbar-track {
    background: transparent;
}
textarea::-webkit-scrollbar-thumb {
    background: rgba(255,255,255,0.1);
    border-radius: 4px;
}
textarea::-webkit-scrollbar-thumb:hover {
    background: rgba(255,255,255,0.2);
}

.controls {
    display: flex;
    gap: 1.75rem;
    margin-bottom: 1.75rem;
    align-items: flex-end;
}

.key-group {
    flex: 1;
    display: flex;
    flex-direction: column;
}

.key-group input[type="number"] {
    padding: 1rem 1.25rem;
}

.actions {
    flex: 2.5;
    display: flex;
    gap: 1rem;
}

.btn {
    flex: 1;
    display: inline-flex;
    justify-content: center;
    align-items: center;
    gap: 0.5rem;
    padding: 1rem 1.5rem;
    border: none;
    border-radius: 14px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.25s cubic-bezier(0.16, 1, 0.3, 1);
    color: white;
}

.btn.primary {
    background: linear-gradient(135deg, var(--primary), #2563eb);
    box-shadow: 0 4px 15px rgba(59, 130, 246, 0.3), inset 0 1px 1px rgba(255,255,255,0.2);
}

.btn.primary:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(59, 130, 246, 0.4), inset 0 1px 1px rgba(255,255,255,0.2);
}

.btn.primary:active {
    transform: translateY(0);
}

.btn.secondary {
    background: linear-gradient(135deg, var(--secondary), #7c3aed);
    box-shadow: 0 4px 15px rgba(139, 92, 246, 0.3), inset 0 1px 1px rgba(255,255,255,0.2);
}

.btn.secondary:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(139, 92, 246, 0.4), inset 0 1px 1px rgba(255,255,255,0.2);
}

.btn.secondary:active {
    transform: translateY(0);
}

.output-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 0.75rem;
}

.output-header label {
    margin-bottom: 0;
}

.btn-icon {
    background: transparent;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    gap: 0.4rem;
    font-size: 0.85rem;
    font-weight: 500;
    font-family: inherit;
    padding: 0.4rem 0.8rem;
    border-radius: 8px;
}

.btn-icon:hover {
    color: var(--text-main);
    background: rgba(255,255,255,0.05);
}

#outputText {
    background: rgba(0, 0, 0, 0.2);
    border-color: transparent;
    transition: opacity 0.3s ease, border-color 0.3s;
}

#outputText:focus {
    border-color: rgba(255, 255, 255, 0.1);
    box-shadow: none;
}

/* Visualization Styles */
.visualization-container {
    background: rgba(0, 0, 0, 0.2);
    border: 1px solid var(--border);
    border-radius: 16px;
    padding: 1.5rem;
    margin-bottom: 1.75rem;
    animation: fadeIn 0.5s ease-out;
}

.visualization-container h3 {
    font-size: 1rem;
    margin-bottom: 1rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.visual-steps {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.step-box {
    background: rgba(15, 23, 42, 0.6);
    border: 1px solid rgba(255, 255, 255, 0.05);
    border-radius: 12px;
    padding: 1.25rem;
    transition: transform 0.2s, border-color 0.2s;
}

.step-box:hover {
    transform: translateX(4px);
    border-color: rgba(59, 130, 246, 0.4);
}

.step-title {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--primary);
    margin-bottom: 0.75rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.step-content {
    font-family: 'Courier New', Courier, monospace;
    font-size: 1.1rem;
    letter-spacing: 1px;
    word-break: break-all;
    color: var(--text-main);
    line-height: 1.6;
}

.char-flow {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-bottom: 0.75rem;
}

.step-char-change {
    display: inline-flex;
    flex-direction: column;
    align-items: center;
    background: rgba(0, 0, 0, 0.4);
    padding: 0.4rem 0.6rem;
    border-radius: 8px;
    border: 1px solid rgba(255, 255, 255, 0.05);
    min-width: 36px;
}

.char-old {
    font-size: 0.8rem;
    color: var(--text-muted);
}

.char-icon {
    color: var(--primary);
    margin: 2px 0;
    font-size: 0.7rem;
}

.char-new {
    font-size: 1.1rem;
    color: #4ade80;
    font-weight: 700;
}

.temp-result {
    font-size: 0.9rem;
    color: var(--text-muted);
    margin-top: 0.5rem;
    padding-top: 0.5rem;
    border-top: 1px dashed rgba(255, 255, 255, 0.1);
}

/* Responsiveness */
@media (max-width: 600px) {
    .glass-panel {
        padding: 1.5rem;
    }
    .controls {
        flex-direction: column;
        align-items: stretch;
        gap: 1.25rem;
    }
    .actions {
        flex-direction: column;
    }
}